Hi Scaffold,
You could employ a UDF in the relevant worksheet's code module, coded along the lines of:
Code:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Static oCell As Range, bVal As Boolean
If oCell Is Nothing Then Set oCell = ActiveCell
If Intersect(oCell, ActiveSheet.Range("A2:C2")) Is Nothing Then Exit Sub
With oCell
If IsNumeric(.Value) = False Then Exit Sub
bVal = (CLng(.Value) = Val(.Value))
If bVal = True Then
.NumberFormat = "#,##0"
Else
.NumberFormat = "#,##0.00"
End If
End With
End Sub
The above will apply your formatting to any cell in the A2:C2 range. Adjust to suit your needs.