The Contacts' "Mailing" and "Other" address fields (Mailing Street, Mailing City, Mailing State, etc.) are auto filled in when I pick the Account Name in the New Contact screen.  They are filled in with the Accounts.Billing Street, Accounts.Billing City, etc data.

I would like to add an extra address field to the Accounts and Contacts modules that captures my customer's "mail stop".  Then, when I pick the Account Name in the New Contact screen, I'd like the "mail stop" field to be auto filled, along with the other address data fields.

What is the best way to do this?  I tried using the Automation->Workflow->Rule with a Field Update, but the Field Update seems to only be able to do a fixed string and not a reference to an Accounts field.

Thank you,

Chris