Can you have one account with multiple usernames that each send tweets to a specific group?

I work for a branch of a non-profit. Head quarters has a twitter acount, but I want to create one specific for our branch. HQ's wants to maintain some control over my branches account. Is there a way to add another username for my branch to the account that HQ has already set up, that can go out to people just in my branch? Or is there some other way for HQ to maintain some control of the account.