Thanks for your reply
i tried like this
var count = parseInt($(button).closest('[id*=dtListOtherItems]').find('[id*=txtOrderQty]').val()) || 0;
$(button).closest('[id*=dtListOtherItems]').find('[id*=txtOrderQty]').val(count + 1);
but its changing whole data list item textbox text
i need only button clicked item textbox