Dave,

You need to use an event.

Copy the code below, right-click your sheet tab, select "View Code" and paste the code into the
window that appears.

This code will make cells with formulas that have been over-written bold and red.

HTH,
Bernie
MS Excel MVP

Private Sub Worksheet_Change(ByVal Target As Range)
Dim NewVal As Variant
With Application
  .EnableEvents = False
  NewVal = Target.Value
  .Undo
  If Target.HasFormula Then
       Target.Font.Bold = True
       Target.Font.ColorIndex = 3
   End If
  Target.Value = NewVal
  .EnableEvents = True
End With
End Sub

You can add this User Defined Function to your workbook.

Function IsFormula(Cell)
   Application.Volatile
   IsFormula = Cell.HasFormula
End Function

Select the range to Format then

Format>Conditional Formatting>Formula is:  =isformula($A1)

I assumed the range was in column A.

Gord Dibben  MS Excel MVP

Thanks for that Bernie,

It does exactly what I want, a couple of things though.......:-)
It appears to have disabled my undo button, I can't seem to undo any of my
often keying errors and if I try to recopy the formula back in to the cell
after I have over keyed, it doesn't put the formula back in only the value of
what the formula would be. I've tried taking the event back out and things go
back to normal

Any suggestions?

Thanks again

Dave