Add this to the declarations section in the userform:

Public Button As MSForms.CommandButton
and then refer to Button wherever you need it in the code.

The ShowDialog code becomes:

Sub ShowDialog(btn As MSForms.CommandButton)
    Dim frm As UserForm1
    Set frm = New UserForm1
    Set frm.Button = btn
    frm.Show
End Sub
and the button_click:
Private Sub CommandButton7_Click()
ScreenUpdating = False

ShowDialog CommandButton7

End Sub