Any suggestions for modifying screen menus with lisp or vlsp/vba?

My intent is to leave the acad.mnu alone and use partial menus for any office specific functions. This works well for specialized functions. However, I would like to modify some of the existing menus (add extra options) for built-in AutoCAD commands such as move and copy. This is simple enough to do with popup menus - but I haven't discovered any means to access the screen menus in the acad object model. Partial menus with the same name do not seem to supersede the acad.mnu. I would rather not undefine/redefine commands as this would defeat the purpose of the partial menus.

Thank you in advance,

Peter