Mass Update of Backup Policies

We have a large number of backup policies created (20-30) and in each policy is set with a different user account for it's Access Credential. When we need to change that user account via Active Directory we currently need to login to AMS and change it manually on each policy.

Is there a way to automate this? Maybe an API to allow our programmers to write something to do this? Maybe a command line utility? I was looking into acrocmd and did not see an option to update policies.

Thanks