Thanks to some guidance from helpful work colleagues and useful input from Brooklands (also MikeCross), I have managed to get my C182 Weight & Balance Spreadsheet doing what I wanted it to do, which was to indicate visually when the W&B data was outside POH limits. This was a bit complex, due to a non-linear envelope.
This is obviously aircraft specific (and is also fairly inelegant Visual Basic code) but if someone is interested in taking this idea and developing it for their own aircraft, I've posted the spreadsheet on my
MSN Group site. It may well be that the guts of the code are re-usable. For those with security settings on their MS Office that warn about macros in the code, it was virus free when it left me!!
I have tested the thing empirically and it has given me the correct results for the data I've entered - it's not guaranteed bomb proof!