Open On Certain Sheet

I have a workbook with several worksheets. I have a macro which runs on opening (to cause a userform to open).

however I am now requiring the workbook to open on a required sheet (still with the userform opening too.

I use the code to open the userform (Module 9)

Option Explicit
Sub ShowMenu()
'
' frmBranchSales.Show
End Sub

On the sheet I want to open to, I have the


Private Sub Workbook_Open()
Sheets("Commission").Select
End Sub

However it will not open.