What regulation covers what an NCO can make you do?

I have a NCO that is trying to say that I have to attened a baby shower this week end. What regulation covers this. I have looked in the DA Pam 600-3 and have no leads. I know they can not make me do this. I have talked with NCO's in another companys and they say its not an Army event that they can not make me go. Any help would be great thank you.