Late Wednesday afternoon, a Swiss money manager for a multinational corporation called a major New York bank and said he wanted the bank to sell 20 million dollars for his company, and buy Swiss francs.

Because the market already had closed in Europe and there was not much interest in the dollar at that time, a bank official warned him that such a large sale could affect the price of the dollar by itself.

But the man in Switzerland insisted. He did agree to set a floor rate on how low he would let the dollar sink before stopping the sale, however. Because the dollar was roughly equal to 1.53 Swiss francs, he agreed to not let the transaction cause it to drop below 1.52.

After 11 million dollars had been sold, the rate dropped to 1.52, and the sales was halted at that level.

"That one transaction was the only thing affecting the dollar that afternoon," said an official of the New York bank involved. "That is all it took to drop the dollar about two-thirds of a percentage point."

The banker used the transaction to illustrate the point that, under certain circumstances, money traders for one or a handful of banks or multinational companies can influence the strength of the dollar. In the case of the bank in question, responsible moneymen succeeded in preventing a major drop in the price of the dollar.

But others contend that there are some not-so-responsible individuals and banks in the money market business who care less for the currency of any individual country, and who will do what is necessary to make big money. Some of these people allegedly have seen fit to beat down the price of the dollar overseas to make hugh profits from the slide.

Green's, a highly respected commodity market newsletter, reported a few weeks ago that the "American bankers ... are the dollar's enemy number one.

"It is enough to follow the daily trading pattern in the foreing exchange market to notice that the traders who depress the price of the dollar and pronounce derogatory statements about the dollar's future have a vested interest in lower quotations for the U.S. dollar in foreign exchange markets," the report stated.

"Most American big banks are heavily short the dollar, and are glad to see it sink because it increases their profits," the newsletter added.

Green's speculated that one way the banks sell the dollar short without having to show they are doing so on their books is through foreign loans.

An American banker gors to a foreign country and offers to loan money to a customer at a more favorable rate than is available from the local bank, for example. After the customer agrees, the American bank sells U.S. dollars for the local currency of the country involved.

Then, when the loan is due to be paid off, assuming that the dollar is lower than it was when the loan was made, the American bank takes its payment in the local currency and converts it back to dollars, only this time getting more dollars for the money. If the dollar has not gone down, then the bank merely turns the money around and loans it to another local company. It keeps doing so until the dollar is low enough for the bank to make money on the conversion alone.

In an unrelated incident, a former money trader for Citibank in Europe has sued that bank for wrongful dismissal, charging that he was let go only because he kept telling bank officials that they were breaking the law in Europe by setting up paper transaction designed only to shift profits from cities like Paris to tax heavens like Nassau.

But David Edwards, who is asking $14 million from his former employer, has raised eyebrows in financial circles for another reason: He wrote an article in MBA magazine describing the activities of a normal trading room in Europe, and implying that many traders for U.S. banks are deliberately beating down the dollar for their own profit.

Edwards' specific charges against Citibank and his general description of international money trading have set off a debate in the financial world over the extent of the power enjoyed by a handful of banks and multinationals that appear to be virtually unregulated in world markets.

"In theory, it is possible for a handful of money traders to influence the price of the dollar for profit," said one top internaitonal money market official for a New York bank. "But I don't think one bank could influence the rate for more than one afternoon."

But he conceded there is the possibllity that a group of banks and multinationals, or even one bank and some of its customers, can influence short-term fluctuations, which can result in large profits. He blames the slide of the dollar in recent months more on "a lack of confidence in the United States, especially concerning the energy policy, trade deficit and inflation.

A high money-market official for another bank was sharply critical of Green's allegations that banks use foreign loans to profit from the dollar's slide, claiming that "his whole argument is shot to pieces when you realize that 90 percent of our overseas loans are made in dollars - not the local currency."

He also contends that, although "it sounds as if there are no controls over world money markets, the network is awfully good. You can't do much on the exchange in London, for example, in any unusual way, without the Bank of England knowing what is going on."

Charles Kindleberger, an MIT economics professor and one of the most prominant authorities on world money markets, says one of the major problems in world money trade is that of traders speculating for banks without telling the banks - or exceeding preset levels for the amount of dollars they are allowed to handle.

Kindleberger was highly critical of the use of tax havens by some banks to whittle down their tax bite around the world.

"I'm very uneasy about Nassau and Singapore," he said. "We have to clean up these tax havens. There is an international good to ber served by doing so. In the long run, we will have to internationalize taxes."

Citibank has denied that it has broken any tax laws. And Thomas Theobald, its executive vice president in charge of international banking, points to the fact that Citibank paid $178 million in taxes during the first six months of this year. "If we're supposedly evading taxes, we're not doing such a hot job," he says.

Theobald also makes a spirited defense of banks' large-scale money trading.

"It is an accepted fact that world trade is billions of dollars a day," he says, "and you need $3 billion in foreign currency simply to sell the day's trade of physical products and commodities. In order for there to be a market in which buyers and sellers connected with his trade can either buy or sell . . . you have to have somebody who throughout the day is willing to put his own money on the stump."

But Theobald admits that there is little or no worldwide regulation of the money markets.

Business Week, for example, reported last week that Chase Manhattan Bank is facing a revolt from its Paris employes. It seems the employes learned that the Chase New York head office has increased the amount it charges its Paris office on the corporate books for "services." The end result is to decrease the profits of the Paris branch by assigning it more of the corporate overhead costs.

All that is fine for Chase, which benefits by having a smaller tax bite in France, but not so fine for Paris employes who, like those of many foreign and domestic banks in France, gain a considerable amount of income from a profit-sharing plan.

According to Business Week, Chase "distributed only 58,000 francs to its 350 employes (in France) this year, based on 1977 profits, compared with 4.1 million francs in 1977 and 2.5 million francs in 1976. That means that, on average, each Chase employe in its French operation received 166 francs this year from profit sharing compared to 11,714 francs last year."

Figures like that are going to make it harder to the banks to keep their employes from taking a long look at overseas operations to see if they, too, are victims of financial manipulation. The secret world of banking may find that more insiders, like David, Edwards, are apt to take their story to the outside if they feel the bank is not giving them a fair shake. No matter if the banks are breaking the laws or not, both sides of the question agree on one thing: There is no effective watchdog on the rapidly growing business of international money trading, and there is a hugh potential for abuse. In fact, the abuse need not be too sophisticated to be lost in the abnormally secret world of banking.