[Closed] how can I make an instance from an xref?

hello to all of you!

I run into a kind of an odd behavior in 3ds Max 2008:

when I want to make an instance from 2 objects I can write:
$obj1.baseobject = $obj2.baseobject

but when I’m trying to do the same with xrefs I get an error:
“– Runtime error: Cannot diretly set a node’s base object” (the spelling error was in the source!)

is there a simple way to make 2 xrefs instances of each other?