How to include “ALL” in a Combo Box

I have a “OwnerName” Query which lists all the Owner Names.
I have a Combo Box with a Row Source linked to this same Query.
The user has the choice to click on ONE of the Owners Names.

But how can I add the option to choose “ALL” the Owners? :S

I have researched the internet but I am not very good at SQL and I am not able to find an easy way to do this or where to put it!!!???