Excel VBA - How to select colums in a specific sheet?

Question

I need to select columns on a specific sheet. Somehow this is not working:

Dim ws As Worksheet
Set ws = Worksheets("Mysheet")
ws.Columns("A:S").Select
Selection.EntireColumn.AutoFit

And simple Columns("A:S").Selectdoesn't activate the sheet I need

Solution

I tested your code and it works fine as follows.

Sub test()
    Dim ws As Worksheet
    Set ws = ThisWorkbook.Worksheets("Mysheet")
    ws.Columns("A:S").EntireColumn.AutoFit
End Sub

No need to Select anything, so I put the two statements together without the Select.

I added ThisWorkbook to (more) fully qualify your ws declaration. Make sure the worksheet Mysheet is in ThisWorkbook otherwise change that to state which workbook the sheet resides in.