Activate sheet after open workbook?

On a command button in a userform, I have this code to open another workbook:

Private Sub CommandButton4_Click()
Dim MyWb1 As Workbook
Workbooks.Open ("C:\pro\anvils.xls")
Set MyWb1 = ActiveWorkbook
End Sub

Now I want to activate the sheet called "HDM Anvils" in the workbook we just opened.

Thanks for any help.