DALLAS (CBSDFW.COM) – Resting in a hospital bed, 7-year-old Zach Guillot is clearly not happy. “I’d rather be out of here,” he said in frustration. This will be the second time that the Dallas first-grader is set to undergo chemotherapy for a rare type of leukemia.

The experience is exhausting. “People are coming in and poking and prodding on you all day long,” said Jeff, the boy’s father.

First diagnosed with leukemia about two and a half years ago, Zach received a bone marrow transplant from his younger brother, Jake. It seemed to work, for a while. But just before Thanksgiving, the symptoms of cancer returned, landing Zach back at Children’s Medical Center.

In some ways, the relapse has been worse. “I call it crushing stress,” said Zach’s mother, Julie. “I didn’t know if we could function through this because it was so stressful, because we knew what this meant – that this is a very uphill battle.”

Doctors are now looking outside of the family for the perfect donor, to give Zach his best chance at help. If the boy relapses one more time, he could be out of options. “He would probably not survive the cancer,” said Dr. Victor Aquino. “This is a life or death matter.”

“You can see me shaking,” said Julie. “I mean, there are days when we’re like, physically shaking.”

In an effort to help, the family is urging people to sign up with the National Marrow Donor Program, knowing that it will likely take the kindness of a total stranger to save their son’s life. “It could save Zach or any other kid here at Children’s this holiday season,” Julie said.

The family is also hosting a donor drive at Zach’s school – Parish Episcopal School, Midway Campus – from noon to 6:00 p.m. on Sunday. Anyone who would like to help out is urged to show up at the event. You can also register online by clicking here.