I have attached another zip file, it is not quite what you want as it is not based on a query. I think it is possible to base it on a query, however I am not familiar with that method, as this method I use, is more flexible, and basically it uses a query anyway, only in that the query is in its text form.
If you open up the query in the attached zip file the query name is "qryAsUsedInModule" if you open it in Design view, and then select SQL view, you will see the query written out in a text statement:
SELECT Contact.To
FROM Contact;
If you look in the module you will see this line:
strSQL = "SELECT Contact.To FROM Contact"
which is exactly the same query.
then if you look in the module code, you will see where it references the "to" field, and uses it to build up the string for the text box.