There are conditions that your outline hasn't addressed. For example:
• FieldA < 120 and FieldB >= 90
• FieldA >=140 and FieldB < 80
And, when your say FieldA-FieldB gets coloured, is this a subtraction of FieldB from FieldA, and the result gets coloured or do you want both FieldA and FieldB coloured without subtraction?

PS: Please don't post questions about the same issue in multiple threads. Discussions merged.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]