When you say "... drawing is open in the editor..." do you mean after the process, you open the drawing in AutoCAD, or do you mean the drawing has opened in AutoCAD DUE TO the process, and the drawing shown/seen in the editor was not updated until you click the editor (natually, you can only do this to the last drawing that was process and left open)? It seems to me it is the latter case, but not very sure because of the rather strange method signature of
db = MyUtility.GetDatabaseAtPath([fileName], [CurrentMdiDoc], ...,... out [Document])
Does this fucntion is meant for returning a side database, of a database of currently opening document? The function's signature gives no hind which one it would return (or, maybe, if the out Doucment is null, then the returned database is side DB?). Judging by CommandFlags.Session, it seems the funxtion actually opens each drawing in the file name list in AutoCAD. If so, if would be better to let the function simply return the document, and its database can alsways accessed via Document.Database property
Now, if each drawing is opened in AutoCAD, each drawing, upon its opening in AutoCAD would become MdiActiveDocument due to CommandFlags.Session, you can simply call Editor.UpdateScreen() at the end of process to each drawing. You only need to call Editor.Regen() for certain changes to be seen, such as Field updated, Overrule applied...
It also seems to me that for the task your code performs could be done a lot faster with side database, instead of opening each in AutoCAD editor.