The Wednesday night drives have become a ritual for Sam and Nancy Enfield of Stafford County. First, they stop at Loudoun Hospital Center, where they pick up vials of blood. Then they go on to the National Institutes of Health in Bethesda, where they drop off the blood to be analyzed.

On the way home, they usually pray. One of the vials just might save the life of their 2-year-old granddaughter, Jackie Lindsay.

Jackie, who lives in Lovettsville, has leukemia. If she receives a bone marrow transplant, she may live to grow up and grow old. If not, her chances are less than 5 percent.

The vials that her grandparents transport each week contain blood samples from people who have agreed to donate their bone marrow to Jackie, a round-faced toddler with downy blond hair and huge brown eyes. But none of the 587 samples have matched Jackie's closely enough to be suitable for transplant.

The Enfields have been picking up the tab for NIH to analyze the samples, which cost $55 each. But they need help from the community.

On Saturday, the Junior Women's Club of Loudoun, the Countryside Commercial and Professional Center, Arundel Publications and Loudoun Healthcare will sponsor a race to benefit Jackie at Loudoun Valley High School in Purcellville. It begins at 8 a.m.

The Countryside shopping center in Sterling also will host a festival at which attendees will be encouraged to contribute and to have their blood tested for a possible match. Money raised will pay for NIH to continue analyzing blood samples.

For the time being, Jackie is living on chemotherapy. Now the disease is in remission, said her mother, Dara Lindsay.

But "she's already had one relapse and once you have, one the chances are greater that the treatment is not going to work," Lindsay said.