HTML Objects - How To Get Element From Document

I've seen lots of examples of invoking the getElementById and they always are given as a method of the document object. That is, they always show something like:
Code:
var theElement = document.getElementById("Fred");
But what I'd really like to do is to get an element from the document, but starting at a particular element in the hierarchy of the document.

For example, suppose I have two forms, form1 and form2, and they both have elements in them named "Fred" (and, yes, I know I shouldn't do that). But what I'd really like to do is something like:
Code:
var theElement = form1Element.getElementById("Fred");
assuming that I've already somehow retrieved the form1Element.

But Javascript reports to me that getElementById is not a method of form1Element. And the fact that every example I've ever seen of getElementById invokes it as a method of document would seem to bear that out. The thing is, on the microsoft site it actually shows the generic form of the method as:
Code:
object.getElementById(iD)

Which would seem to imply that it's more generic than just being a strictly document method, that perhaps it's intended to be a method of at least some additional HTML objects. Since that doesn't seem to be the case, how might I go about doing what I'd like to d, which is find the occurrence of the element, by its ID, but only within a particular section of the document hierarchy?