In order to eliminate only epub head of print, add the following at the end 
of your search:

NOT pubstatusaheadofprint

Steve - if we restrict to medline subset, we are eliminating other citations 
that are printed but not yet assigned mesh

For eg
diabetes AND 2009[dp] NOT pubstatusaheadofprint gives me 21883

Whereas if I do
diabetes AND 2009[dp] AND medline[sb] (that is limiting to medline subset), 
it gives me only 18483

If I do a boolean NOT of the two sets :

(diabetes AND 2009[dp] NOT pubstatusaheadofprint) NOT (diabetes AND 2009[dp] 
AND medline[sb])

I get 3400 articles, and all of them are "In process"

Hope this helps

Vasumathi Sriganesh
CEO, QMed Knowledge Foundation
Chakala, Andheri East,  Mumbai 400099, India
Web: www.qmedkf.org.in    Indian Medical Sites- www.indianmedicalsites.in