Compact letter display for interaction effects

Hello,

I am interested in generating a compact letter display for the results 
of Tukey HSD tests that contain interaction effects. The 'cld' method in 
the 'multcomp' package seems only to work for main effects. Does such a 
thing exist already? Thank you for any thoughts,

Josh

Joshua Caplan, PhD
Postdoctoral Associate
Department of Ecology, Evolution, and Natural Resources
Rutgers University
14 College Farm Rd, New Brunswick, NJ 08901
p 732-932-9383   f 732-932-8746
jcaplan at aesop.rutgers.edu