The return from (nentsel) for a nested object ends with a list of what it's nested in, starting with the deepest-nested one and stepping up from there.  So if [for example] you pick on a part of a Block in that Xref, you'll get the file name and Block name in "TWO|test" form, not just the Xref drawing file name -- maybe that would serve your purpose.  But if you pick on a Dimension, you'll get something like "*D|REF6", which presumably would not.