I have trouble on Gridview pageindexchanging and select with update panel

When i create modal popup. Inside modalpopup, i have update panel and gridview. Inside update panel have gridview. When i need pageindexchanging, it works. but when select can't entry field on textbox.
Because i want, select gridview is event postbcak, and pageindexchanging evet asyncpostback. Ohh I don;t have answer to do this