ModalPopup Issues

Hi guys, I followed the advised posted in this thread http://www.sitepoint.com/forums/showthread.php?t=670401, but I noticed that once I clicked on the Nth page of the gridview control, the position goes at the bottom of the web page. Another thing is, I cannot get the value being selected in the gridview; say for example, I’d like to display the ID of the person in the textbox after I click on the gridview control.