You want to base it on when the user clicks on the tab control, the code determiens what the current tab seelcted is and takes appropriate action. see the code below.

Private Sub tabClient_Click(PreviousTab As Integer)

Select Case tabClient.Tab
Case is = 0
cmdSave.Visible = False
cmdOpen.Visible = True
'put some code here to do your database work or better yet
'use a called procedure
Case is = 1
cmdNew.Visible = False
'put some code here to do your database work or better yet
'use a called procedure
End Select

End Sub