<oPopUp>:getShortct(<nInkeyValue>) --> nPosition

        <nInkeyValue> is a numeric value that indicates the inkey value to be
        checked.

        Returns a numeric value that indicates the position in the pop-up
        menu of the first item whose shortcut key matches that which is
        specified by <nInkeyValue>.  The shortcut key is defined using the
        MenuItem:shortcut instance variable.

        getShortct() is a method of the PopUpMenu class that is used for
        determining whether a keystroke should be interpreted as a user
        request to select a particular pop-up menu item.