how to capture CTRL+

From reading the source for onkeypress and onkeydown, it seems not possible to receive Ctrl+ and Ctrl- (keycode == 0 and charcode == 43 or 45). Am I mistaken or this is a bug?

You can still use setEvent method -

obj.setEvent("onkeydown", function(event){
    if (event.ctrlKey) {
        switch(event.keyCode){
            case 107:
                alert('plus');
                break;
            case 109:
                alert('minus');
                break;
        }
    }
});

Thanks.
I refined my need to a more general need where I want a listener per grid to capture Ctrl+ and Ctrl- document wise in order to zoom in or out each grid header and rows height. This way I can work around the height specification in "px" - Specifying column width in "em" using style seem to workf well.
I finally found a solution to this.