With a hatchling, don't panic for another week at least. You're little guy can probably go a full 2 months without food, and maybe more. Of course, you don't want him to go that long, but just remember that you have time.
So the first thing I need to ask is what are the temperatures in the cage? How long have you had this hatchling, and do you know if he was eating before you got him? This is all very important to figuring out why he's not eating. What are you feeding him, and how often are you trying to feed him? Finally, what techniques have you tried to get him to eat? Have you tried live, braining, or cutting the mouse, or have you just changed the conditions in his cage?
If you can post all that, then hopefully I, and the others on the forums, can give you good idea of what to try next. If that's not enough info, don't worry, I've got a few more questions up my sleeve.
I hope I can help!!