PokerTracker

I want do make some reports which show me the averages of some stats under certain circumstances (e.g. ftp 2-table-turbo tourneys between 12 and 4 PM on working days ;) ). For a stat like raise flop CBet or fold to pf 3bet i need a certain number of opportunities or facings, to have a reliable denominator. Just looking for people with more than xxx hands doesn't really work, because one guy needs 100 Hands to get raised 10 times on the flop, and the other needs 500. Can i by some stat magic create stats, that don't show a number, if the denomitator is below xx? And by this way filter out these values when creating averages in the report? Or do i have to do a single report for each stat with an appropriate column filter?

You can do this using an IF statement in the Format Expression of your stat.
This sort of thing is explained in Kraada's excellent How To: Advanced HUD Configuration - actually, in this post in the same thread.

Does this work also together with report summaries? Meaning, while computing the averages, the "non-values" (where the denominator is below xx) wouldn't count?

You'd need to put the statement in the Format Summary Expression but then it should work for the summary as well.