How Do I Test For HTMLImageElement In IE?

I have the following code that test the target element of a mouse
movement to check if its and Image and the Parent is a Div element. It
works perfect in Fire Fox, however IE does not allow access to test the
target against instance of HTMLImageElement or the Div Element.

Is there a property that I can use to get the object type that will
return "image" or "div" or anthing else that I can use. The typeof
function only returns "object" which is totally useless in my
application.

DragObject.prototype.mouseMove = function(ev){
ev = ev || window.event;
var target = ev.target || ev.srcElement;
var dragObj = target.getAttribute('DragObj');

if ( target instanceof HTMLImageElement && target.parentNode
instanceof HTMLDivElement){
target = target.parentNode;
dragObj = target.getAttribute('DragObj');
}
}