I'd recommend using JQuery's keyup and keydown methods on the document, as it normalizes the event codes, to make one solution crossbrowser.
For the right click, you can use oncontextmenu, however beware it can be buggy in IE8. See a chart of compatibility here:
http://www.quirksmode.org/dom/events/contextmenu.html
Click me
$(document).keydown(function(event){
if(event.which=="17")
cntrlIsPressed = true;
});
$(document).keyup(function(){
cntrlIsPressed = false;
});
var cntrlIsPressed = false;
function selectMe(mouseButton)
{
if(cntrlIsPressed)
{
switch(mouseButton)
{
case 1:
alert("Cntrl + left click");
break;
case 2:
alert("Cntrl + right click");
break;
default:
break;
}
}
}