You will need a bunch of "if-then" statements to define the acceptable
envelope(s). Look it up on Excel Help. Lotsa luck though as the same
guys must write the help as write the original software package.

Note that you can nest "if-then" statements (I recall up to 7 in my
Excel) so that in one long statement you could establish a valid
envelope with up to 7 separate boundaries.

An interesting challenge! Good luck.