I apologize for the abrupt visit earlier — I was running an errand for the department head. Allow me to properly introduce myself.

I ran an errand to the neighborhood greengrocer and forgot my wallet!

I stepped out during the meeting to make copies on the section chief's behalf.

You want me to go run another errand? You've got to be kidding!

In the evening, I delivered some documents to a client on the department head's behalf.