function on key combination

[TOTALCAPS]

i had make a listener that on tab(9)key up it execute a function that moove the focus of the blinker in a list of textfield .

What i want to do is to execute an other function when the user have the shift button down and press on the tab so that the focus will go backward ...

is there a way to combine to key in a listener

tableListener = new Object();
tableListener.onKeyDown = function() {
acKey = Key.getCode();
};
tableListener.onKeyUp = function() {
if (acKey eq 9 or acKey eq 13) {
sectionTable.move = "tab";
sectionTable.setInputFocus();
}
};

any help will be apreciate!!

Thanx