User Defined Function Fails when I run a Macro

[scott altman]

I have borrowed a UDF from another site. It has the simple function of finding the text color in a cell. It works perfectly when I use it as part of a formula. Here is the UDF:

Function txtColor(rng As Range)
txtColor = rng.Font.ColorIndex
End Function

I have a macro that filters cells based on the a formula using this UDF. When I filter using this formula by hand, the filter process works fine. But when I use my macro -- which filters, then copies, then pastes, the formula no longer works. All cells containing that formula transform into #VALUE!.

Thank you in advance for any suggestions.

Scott