You can restrict all scripts to certain categories by adding Cat=1,2,4,8 etc.. into the URL.
So I supposed you could hardcode the Cat variables that you
do want them to search into the recent post links.
The only trouble with that would be that then, every link you click after that would pass those same Cat variables - thus preventing them from seeing that category. If you're not using the Cat variables anywhere else, you could then just hardcode Cat=0 into the "Main Index" link so that they'd have an easy way back to see all forums.
