Donna Price says that if her 2-year-old daughter Marjorie ever gets lonely, she can wave out the window of her new Rockville day care center and say, "Hi, Daddy!"

Daddy, accountant Donald Price, works across the street at Shady Grove Hospital. Knowing that "Daddy" is so close "is very, very important" to their daughter, said Donna Price, a public relations assistant at Martin Marietta Corp. in Bethesda.

In the meantime, she said, "we plan to drop in occasionally to see what's going on."

The new center on Broschart Road is in the heart of a 300-acre prairie of research and medical facilities called the Shady Grove Life Sciences Center, which the Montgomery County government intends to develop into a major employment complex.

The day care facility is the first of 17 modular centers the county hopes to erect to help satisfy the growing demand from parents. An estimated 48,000 children require day care in Montgomery alone, but only a third of them are supervised by any of the county's registered and monitored care providers, according to county officials.

The Shady Grove center, a 29,000-square-foot, one-story building with brown brick veneer, was created in a factory, assembled on the county-owned site in three days, and cost $147,000. The modular structures also can be taken apart and moved to other locations. "We could pick it up and move it if we wanted, but we think it will stay here for a while," said Robert Maddox Jr., who was in charge of the project for the county.

Operated by the Treatment Centers for Disabled Children and Adults, the center opened in mid-July for children of anyone working or living in the county. But, despite the pent-up demand for day care in Gaithersburg and Rockville, according to county surveys, the center has enrolled only 10 children, about a fourth of its capacity.

Staff members said they believe that many parents in the area already had made child care arrangements for the summer, and said they expect enrollments to pick up shortly.

"It will be better at the beginning of the school year," said preschool senior staff member Patti Feldman. "We've been getting lots of phone calls."

For now, Marjorie Price's only schoolmate in the preschool half of the facility is Wesley McKutchin Jr., 4, whose parents switched him from another school. His father Wesley Sr. is an accountant at the Hewlett-Packard & Co. office on nearby Shady Grove Road, and his mother Diane is a broadcast technician for WJLA-Channel 7 in Washington.

Like the Prices, they now are able to drop their child off on the way to work without much of a detour.

Wesley Jr., interviewed in the midst of absorbing a spaghetti strand into his mouth, said he was having a good time at the new school. Marjorie Price, when asked what she was having for lunch, replied, "Foods!"

They had spent the morning with their teachers -- for the moment, there is a 1-to-1 ratio of staff and pupils in the preschool side of the school -- engaging in play designed to teach them things painlessly, such as the difference between right and left.

The next modular day care centers are expected to open this fall at the Martin Luther King Jr. Park near White Oak and at the new S. Christa McAuliffe Elementary School in Germantown. Both will provide before- and after-school care for school-age children, said C. Bennett Connelly, chief of the county's Division on Children and Youth.

Some day care center operators say that despite an infusion of county funds and intensified interest in recent years, Montgomery has fallen far behind counties in Northern Virginia in opening day care facilities. That is partly because Virginia day care laws are less stringent than Maryland's and because no corporate leaders or congressional representatives have taken the lead to encourage business-sponsored facilities, the care providers said.

In Montgomery, no large corporation has offered its employes facilities for child care, even though the availability of such services is, increasingly, a factor in attracting clerical and professional employes. The main concern of companies, said Jack Harris, chief scientist at the Tracor facility in Rockville and a member of the county economic advisory council, is "the liability they would be open to" for charges brought against day care center employes or insurance claims.

In Fairfax and Arlington, large corporate-sponsored day care centers have opened, but have circumvented the liability question by placing the responsibility in the hands of independent, nonprofit operators.

Harris said the impetus for creating the modular units in Montgomery came from workers calling the county and saying, "I have a problem."

Opening the first modular center "is in many respects a big step," said Frances Abrams, president of the Child Care Connection, a referral service for Montgomery County parents. "One of the most critical needs is for space," she said. "It's very difficult to find new space . . . in Montgomery. Every available classroom and every available church, community room . . . is already being used for child care."

But by assembling prefabricated units that are designed specifically for child care, "I would like to think that the county is modeling something that can be used by others in the community," including developers or builders of subdivisions and office buildings, "who really want to provide this kind of service," Abrams said.

This is a kind of "no muss, no fuss" installation, she said. "You simply have to install it and lease it."

Charges at the Shady Grove center range up to $175 a week for infants and up to $85 a week for preschoolers. One parent, Judy Potasznik, said that was comparable with what she paid when her son Max, 2, was cared for at home.

But she said she felt lucky to have found the place.

"In terms of finding good quality care in or out of the home, it's catch as catch can."