<<Disclaimer:  Verify this information before applying it to your situation.>>
 
This is from Bette Hagman's book "More from the Gluten-Free Gourmet" under
Substitutions for other Intolerances and Allergies.
If you are lactose intolerant, in baking bread, substitute one of the
powders found in health food stores:  Lacto-Free or Tofu White (both contain
soy) or NutQuik (made from almonds).  Another choice could be a powdered baby
formula from a supermarket or drugstore:  Isomil, ProSobee, Nursoy (all soy
based) or Pregestimil (corn based).