Would you settle for a double-click?
Private Sub Worksheet_BeforeDoubleClick( _
ByVal Target As Excel.Range, Cancel As Boolean)
Cancel = True
With Target.Interior
.ColorIndex = IIf(.ColorIndex = 3, xlColorIndexNone, 3)
End With
End Sub
You could do the same thing with a single click by using the
Worksheet_SelectionChange() event macro, but that would also be
triggered by tabbing, the Enter and arrow keys, etc.