Textbox focus

We have a web page with a Textbox server control, when we click on the tetxbox (id= txtEJDate) on the form the focus is set to the Textbox, but when we tab on to it, it does not get focus and none of the other controls on the form get focus.  In the VB codebehind we have the following txtEJDate.Attributes.Add("onfocus","this.select();return onSelected();"). This is the only control on the form that behaves this way, when we tab to any other control on the form they retain the focus.  Not sure what's different?