Is the pain always there?
Does it start up from step one or does it start up later in the run?
Is it there after the run?
The reason I ask is that it may be chemically based or injury based or even nutrient based.
Stretching may or may not help.
anyway
here's two links for calf stretching.
one is straight-legged for the gastrocnemius.
one is bent legged for the soleus.
you need to do two stretches to totally hit the calf.
http://www.dcdoctor.com/pages/rightp...k_st_calf.html
http://exercise.about.com/b/2008/07/...lf-stretch.htm