Hmm… I’m actually unsure how you would do that. This post doesn’t seem to give any real solution to such a problem even though it’s indirectly mentioned. The introduction post for the asset escrow doesn’t say anything about this either.
Maybe you could probably ask on the discussion page of the forum, someone else probably has encountered the same issue.
Sorry that I couldn’t give you a proper answer on this one, I just don’t actually know myself.