I´ve done a small example, complete with model and a stripped down script.
Just the main() and the action for the model.

Here you go [254 kb]:
http://www.vulkanware.de/stuff/Test7Bonerotate.zip

You can rotate the bones with the cursor keys.

Again, thank you very much for looking.
Perfect would be a function like "ent_bonerotate_to(ENTITY* ent, STRING* szBone, VECTOR* vPos)"

no science involved