Hi,

A quick but not ideal way would be, to have your formula replaced by :
=IF(isnumber(A1),1,0)

But ideally, it would be better to have the formula
=IF(isdate(A1),1,0)
and add in one of your modules :

Function IsDate(Var As Variant) As Boolean
' from Chip Pearson
IsDate = VBA.IsDate(Var)
End Function


HTH
Cheers
Carim