[OS X TeX] autogenerated cite keys; BibDesk 1.3.20

[Alessandro Languasco]

Hi,

I'm trying to autogenerate cite keys in BibDesk using the following  
custom format

name of the first author + first initial of the surnames of the  
remaining authors + year + progressive letter

The best result I am able to get is to use the commands

%a1%a91%Y%u1

but the first letter of the first author is repeated.
The problem is how to distinguish the first author among the others  
using
the commands explained in BibDesk's help.

To use the example in Bibdesk/Cite Key Format preferences: this way I  
get

McCrackenMMHPHRS2004a

while I would like to get

McCrackenMHPHRS2004a


Do you have any suggestion? Thanks a lot !

Alessandro