Actually, there is a CF adapter to increase the range, by about 60ft. Check
Here It works the the iPAQ pocket pc, but thats all it says. I don't see why it wouldn't work with other PocketPc's though, or maybe they just haven't tested it on any other PPC yet? Who knows...
Hope this helps.
Adam
EDIT: Now that I read the FAQ about it, here is what I found:
Q: Will PDA-ir work with my Dell Axim?
A: No. This is a software issue. PDAwin is working on this issue currently.
So, I guess the answer is no, there is no IR range booster for the Axim currently...Sorry