bring focus to form element using VB .NET 2003

I have an web form that I created in VS .NET 2003. On
this web form, there are check boxes and radio buttons.
Utilizing AutoPostBack=TRUE, when a specific check box is
selected, a text box is displayed to the visitor. When
it is unchecked, the text box goes away. All that works
like I want it to. However, because I am using
AutoPostBack, the form reloads and brings focus to the
top of the web form. I would like to bring focus to the
text box. I do not wish to use javascript. Does anyone
know of way to bring the focus to the text box?

You suggestions or recommendations are appreciated.
Thank you.