Custom properties on xmlhttp object

Say x in a XML Http Request Object ... meaning it's either XMLHttpRequest (firefox) or ActiveXObject (IE)

This line of code works in firefox...
x.someProp = "someValue";
alert(x.someProp);

But in IE I get "Object doesn't support this property or method"
I need to place a custom property on the object.
Is there any way I can do that in IE?

I've already tried ActiveXObject.prototype.someProp = "";
That doesn't seem to work in IE.

You can not extend the object with IE.

You should look at coding with OO JavaScript instead of trying to do something similiar with this custom property,

Eric