Modifier key recognised with an ahref/onClick event?

Hi,
I've been trying to get an onclick event to check for the SHIFT key and branch accordingly. I've had limited success, finding no robust script to do this cross browser/DOM. I posted a thread a short while ago, but had no responses; there is more information about what I am looking for there: Previous thread (http://www.codingforums.com/showthread.php?t=69531)

Anyway I did some more searches on the forums & found this script which checks for a click event in the document. It seems to work across a good proportion of modern browsers.

Could anyone tell me how I can successfully use this on a standard <a href"#"..> link?


document.onclick=function(e){
if (!e) e=event;
if (e.ctrlKey){
alert("CTRL key is pressed.");
}
else if (e.shiftKey){
alert("SHIFT key is pressed.");
}
else if (e.altKey){
alert("ALT key is pressed.");
}
else {alert("Single click.");
}
}

Any help/advice would be much appreciated,

RJW.