You would use conditional formatting. Assuming you do not want to format the
cell if it is balnk they use a formula similar to this...

=AND(A1<=NOW() - 30, A1<"")
otherwise you can just use Cell value is and choose less than or equal to
and add
=NOW() - 30
--
HTH...

Jim Thomlinson


"Alexa M." wrote:

What I want to do is, when I open up excel I want a date to change colour if
it is overdue (Ie thirty-one days from the invoice date). Would I use
conditional formating or would the IF Function be better suited for this?
--
Alexa