Sub Button1_Click()
Dim LstRw As Long, rNg As Range, c As Range
LstRw = Cells(Rows.Count, "F").End(xlUp).Row
Set rNg = Range("F1:F" & LstRw)
Application.ScreenUpdating = False
For Each c In rNg.Cells
If c = 1 Then
c.NumberFormat = "@"
c = "00"
End If
Next c
End Sub