I think we need a more information.
One way to get to the end the document using only Range is as follows. The
Select() is added so you can see where you end up.
rng = ActiveDocument.Range;
rng.MoveToDocumentStart();
rng.SelectContainerContents();
rng.Collapse(sqCollapseEnd);
rng.Select();
This gets you there as well:
docNode = ActiveDocument.documentElement;
rng = ActiveDocument.Range;
rng.SelectAfterNode(docNode);
rng.Select();
Or this:
rng = ActiveDocument.Range;
rng.MoveToDocumentEnd();
rng.Select();
There are probably many other ways. Are these even close to what you are doing?