I ran the following code to validate if a user has entered a number.
The problem is when the cells interior color are changed, the undo and
redo buttons become non functional. What can I do to make them
functional and still highlight a cell with an invalid entry? When
cells are validated using Excel's validation, the undo and redo
buttons still work OK. How do I highlight a cell like in Excel's cell
validation? Is there another way of highlighting?

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
If IsNumeric(Cells(Target.Row, Target.Column).Value) = False
Then
Cells(Target.Row, Target.Column).Select
Cells(Target.Row, Target.Column).Interior.ColorIndex = 4


Thank you
John