AutoCAD .NET :: MDI - Iterating Many DWG Files

I'm working on translating a VBA routine that worked just fine, to VB.NET & I have had a lot of porblems with it. Yes, I am new to VB.NET. My routine renames XREF file names & opens  drawings that have these files XREF'd into them & resets their paths to the renamed file. My VBA routine used a few thisdrawing.sendcommand operations to do things like reload xrefs, unlock layers etc. Some of these worked in the VB.NET version while I only had getten as far as having the only DWG open that  was the one which I call the routing from. When it gets into opening another drawing I start getting all sorts of problems.

I worked these out by creating a NEWDOC as DOCUMENT object & setting autodesk....MDIcurrentdocument to the filename of the just opened DWG file &  then eliminating my sendcommand calls & replaceing them with record table operations.

Now I'm getting a file access error when trying to reload an XREF using document.reloadxrefs(objectidcollection).

I've tried not to nest transactions. I've tried to make sure all my transactions frpm  the current DWG not the original.

How to work with multiple DWG files. Maybe a simple example of reloading an XREF named "X" in a bunch of DWGs saved at some specific location could be given? Focusing on transactions, documents, & databases.