text box focus on asp.net ajax

Hi,

I have a signUp form in asp.net (web form)

I check User Name is reserved or not in text-box text changed (with ajax)

but when user enter a key and text changed event occure,

text box loss cursor. and when I focus on text box (in text-changed event), the cursor come to first of text boxInstead of being in end of text.

I hope that was clear :)

Thanks alot :)