Topic: acts_as_audited append text onto end of audit_changes

I have the acts_as_audited set up and running fine. But, if the password gets changed we want a piece of text that says it was changed appended to the end of the audit_changes field instead of showing old and new values.  The boss does not want to use the existing comment field for this as we are using that for something else.

How can we go about this?