Thanks, You Splitter for the background. Hope the cold sweats don't last. Nice of you to give CHORES! the "Simple? Yes, but effective" testimonial.
Ialapanzi, to do the high hours the way you suggested is achievable, but of course would involve you entering all the data twice: first entering the planned roster, then the actual flight data once they have flown. In practice, if You Splitter breaks into cold sweats at the thought of entering data once, there is not going to be much enthusiasm for double entry. Too much like accounts, and CHORES! was designed to minimise data entry.
The practical workaround is to A) - run the High Hours scan today after all yesterday's returns have just been entered. Now you know if anyone is close to any of the totals for scrutiny, and which ones. Now B) - run the boring totals diaries for these few exposed crew members into the week ahead. Of course the totals will gradually reduce towards zero as the stuff of last week/ 2-weeks/ 4-weeks/ 28days etc gets subtracted and the future rosters haven't yet been input, so you now know how much increasing flex each individual has on each of those days ahead. C) - make the comparison with the rosters.
Luckily, the rostering has often been done in the form of lines of work or "crew routes" whose hours flying / duty content is already calculated and similar every week or day. With those ready roster figures and the reducing totals diaries to hand, with a tad of numerical agility you can now spot any forthcoming crises. It is often obvious: Eg, 99 high 28-day flying hours today, down to 95 forecast day hours tomorrow, so that's ample flex for doing an Ibiza without busting 100hrs (but not for doing the Tenerife). Hope all that makes sense!
In a full rostering system this would be automated and you wouldn't have to do it yourself. Sorry Wanderlust, don't know of a simple cheap rostering system. But do have a look at the one syd_rapac mentioned - (thanks, Syd) -
http://www.forte.co.nz/Geneva/GenevaFrame.htm
awesome marketing. Feels like a tad more expensive than Ialapanzi's spreadsheet...