${TriggeredValue} variable is always empty

Hi,

I am trying to determine what value triggered every alert.   The documentation refers to the ${TriggeredValue} variable for this but it doesnt seem to return anything.   Is there anyway I can determine this from the variables?   For example if I have a node alert, I'd like to know from the variables if CPU Load triggered it or if Available Memory triggered it, etc...

Thanks

J-