In Excel 2003....

I have been asked to look into changing the color of the arrow on an
autofilter tab for a filtered cell from blue to some other color so it can be
more easily distinguished from the black tabs which are not filtered.

I know the actual color of the arrow cannot be changed. However, is there
some formula (like ISERROR() only ISFILTERED()) which can be used to see if
an autofilter is engaged on a particular cell?

I have also tried using VBA and conditional formats to change the color of
the Header cell when a filter was being used, but this is a shared workbook,
and when I was testing it out, I received an error(However, it did work when
the workbook was not shared).

Any help or suggestions would be much appreciated.