I run this question again.
I am novice in VBA so I have no idea how to make User Defined Formulas
as written i earlier discussions.

I have cells with formulas picking up data from a linked file.
On and off I overwrite the cell formula with figures (1234).
Then I want the conditional formatting to change the cell color
to remind me that I have overwritten the formula.

I suppose the answer still might be VBA, but can you then explain to a
novice/rookie how to do it?

Regards,
Claes