title: intercept select all checkbox event on client grid
body: <p>I have a client radgrid with a select column and some other columns. when the select all checkbox is checked it attempts to check all rows in the grid. I didnt want it to select every row unless it obeyed certain conditions so I added some javascript to do this. 
  Because it potentially doesnt select all rows, the select all check box wont be selected. I want to check the select all checkbox here so that when it is unchecked, it will remove all the selected rows.
  Looking for a way to get the click event of the select all checkbox or something similar. I don't believe there is an OnClick event assoicated with it but i could be wrong?</p>