Sub toto()
Dim montableausource
Dim x As Integer
montableausource = Range('B2:B' & Range('B65536').End(xlUp).Row)
For x = 1 To UBound(montableausource)
montableausource(x, 1) = Left(montableausource(x, 1), 5)
Next
Range('B2:B' & Range('B65536').End(xlUp).Row) = montableausource
End Sub