I\'m using jQueryUI autocomplete, and I have a function mapped to the select event, e.g.:
$(\"#someId\").autocomplete({
source: someData,
select: fun
Simply call following function
setAutocomplete("#txt_User_Name","rohit");
function setAutocomplete(autocompleteId,valuetoset)
{
$(autocompleteId).val(valuetoset);
$(autocompleteId).autocomplete("search", valuetoset);
var list = $(autocompleteId).autocomplete("widget");
$(list[0].children[0]).click();
}