// Create the event handlers for PageRequestManager
var prm = Sys.WebForms.PageRequestManager.getInstance();
prm.add_beginRequest(PageRequestManager_beginRequest);

var uiId = '';

function PageRequestManager_beginRequest(sender, args)
{
var postbackElem = args.get_postBackElement();
uiId = postbackElem.id;           
postbackElem.disabled = true;
}