function document_onkeydown() {

           iKeyCode_Enter = new Number(13);

           if (event.keyCode == iKeyCode_Enter){

                var oControl = document.getElementById('NAME_OF_CONTROL_TO_CLICK_HERE');

                if (oControl != null){oControl.click();}

                event.cancelBubble = true;

                event.returnValue = false;

           }

     }