formula wont update

Kevin,

Thanks for your help, but I am afraid it still does not update.

I now made the formula:

Function BookExists(wb As String)
Application.Volatile
BookExists = Len(Dir(wb)) > 0
End Function

Did I understand you correctly?

I still have to edit the cell with the formule (F2) and press enter.

regards,
Arien

Sorry my mistake. It does work now.

Thanks a lot

regards,
Arien