Inverted pqact.conf matches

Is there a way to match everything EXCEPT what you specify?
For instance, I want to put some PIREPs in a couple of different files so I have 

^UAPA.*
FILE ......

^UBUS.*
FILE ......
and then I want to match everything that starts with a U but doesn't match the rest of the above. Any ideas? I'm coming up blank. 

Thanks.

A Cline