If I'm thinking of your problem correctly - you want to later (perhaps in
another function) - pull this dynamically  created control  out of the page's
bag-o-controls & use it. If this is on the right path, then you can use the
FindControl method  of the Control class...

Control myControl1 = FindControl("TextBox2");

Then you can use myControl1 just as you would use (in this example) the
original control, TextBox2