Not sure what limitations might exist in the free version but here you go...
First make sure your selecting the right control. You might be selecting the text object and not the "Textbox" object
[attachment=2:1lgc5vle][/attachment:1lgc5vle]
Then you need to add the action to the event sheet.
[attachment=1:1lgc5vle][/attachment:1lgc5vle]
You will find it here in the action window
[attachment=0:1lgc5vle][/attachment:1lgc5vle]
Hope this helps...