A few years ago I read this neat way of filing controls in this situation.
(Multiple patients with the same sp. stain).  Use a blank slide to file for
the control for all but one of the patients. For the last patient, label
the control slide as usual.  Label all of the other blank slides with the
special stain that was done and the number of the case.  Then below that
information give the number of the case that the special stain control is
filed with.  (Say--sp stain control filed with XXXXX)

If I havn't made this clear, just give me a jingle by E-mail.

Priscilla in Central Wyoming