Try it this way
=======
Option Explicit

Sub counterif()
Dim ms As Range
Dim i As Long
Dim count As Long
Dim x As Integer

Set ms = Selection
x = ms.Rows.count
For i = 2 To ms.Rows.count
Cells(i, Selection.Column) = "MUSA_" & _
Format(i, Application.Rept("0", Len(x)))
Next i
End Sub
========
--
Don Guillett
Microsoft MVP Excel
SalesAid Software

"dan dungan" wrote in message
...
Hi Don,

I'm testing this to better understand how vba works.

When I run this procedure it returns "Variable not defined".

So I added to the procedu

Sub counterif()
Dim ms As Range
Set ms = Selection
Dim i As Integer

For i = 2 To ms.Rows.Count
Cells(i, Selection.Column) = "MUSA_" & _
Format(i, Application.Rept("0", Len(ms.Rows.Count)))
Next i
End Sub

Now when I run it the procedure returns:
Compile error:
Variable required--can't assign to this expression

Format(i, Application.Rept("0", Len(ms.Rows.Count)))

.Count is highlighted.

Dan