Disable single key input in flex

Question

I have an AdvancedDatagrid built up dynamically basing on xml data retrieved from http services. The last row contains columns totals and to simulate its footer behavior it has been foreseen a custom sortFunction, but it doesn't works for multiple columns sorting. Since I don't need multiple columns sorting, I preferred to:

• set adg.sortExpertMode = true;
• extend sortItemRenderer in order to hide the number indicating the sort order and so to avoid user to think multiple sort is possible

Now, my problem is that if a user presses CTRL key and click on 1+n column, the standard adg class foresees the multiple sorting. So I thought I would be possibile to catch the pression of CTRL and to eliminate its effect.

Below the code

private function keyHandler(event:KeyboardEvent):void{
if (event.ctrlKey == true){
   event.stopImmediatePropagation();
}
}

It doesn't work, is there a way to make it possible?? THanks in advance!

Enrico