I am not sure I entirely understand your problems but could you not achieve
what you want using Data Validation?

"jhs626" wrote in message
...
I have a VLOOKUP formula (B5) referencing adjacent cell (B4). If the user
chooses to override the value in the default cell (B5) I want the default
cell's fill color to turn red.

e.g.
if user enters "32" into cell B4 (which is an empty cell to begin w/) the
VLOOKUP formula in B5 checks another wrkbook and returns the default...
say
".09".

the user chooses to ignore the default ".09" and enter in ".5" I want the
format to automatically change the fill color to red.

Any help greatly appreciated.
--
JS