You may be able to use an on focus event to do this. If you select a tab page in the form designer, there is a GoTo Control ID you can set for it. This sets focus to that control when that tab page is displayed. If you set an on focus event for that control it may work. If tabs are needed we typically recommend not using tabs at all and hiding them on your form, instead using button navigation to flip between pages. You could then use an on click event for that.