input毎のidをgetElementByIdで指定せずとも辿っていけた
<form id="form1" name="form1" method="" action=""> <label for="mxx">mouseX:</label> <input type="text" name="mxx" id="mxx" /> <label for="myy">mouseY:</label> <input type="text" name="myy" id="myy" /> </form>
window.onload=function(){
mouseXY=document.getElementById("form1");
}
document.onmousemove=function(e){
mouseXY.mxx.value=e.pageX;
mouseXY.myy.value=e.pageY;
}