[Zope] How to use manage_clone right??

Hi, I've got a problem with the manage_clone function. I used it several times before, but this time it's something special. Normally you clone an object like this, where 'mydoc' is the the object and 'new_id' the new name of the cloned object: <dtml-call "manage_clone(mydoc, 'new_id')"> In my special case, mydoc is not the object itself, but a string of the objects name. The function now can't clone, because mydoc (the string) is not an object and returns the error message AttributeError: cb_isCopyable So how can I clone an object by calling the manage_clone function with the variable 'mydoc'??? Thanks for help Marc