Dear tom
as i understand it 88312 is to be used for each stain that contains 
organisms, silvers, gram, etc while 88313 is for the others like mucin, pas. 
If this is incorrect i am sure the good people of histonet will let me know., 
however if you do three gram stains on 1 casebut three different blocks you 
can only charge once.
                                                     Dana