A family of Microsoft relational database management systems designed for ease of use.
I've posted an amended version of your file to my OneDrive folder at:
https://onedrive.live.com/?cid=44CC60D7FEA42912&id=44CC60D7FEA42912!169
The problem was that the RowSourceType property of the combo box was a Value List. Changing this to Table/Query and setting its RowSource property to an SQL statement, allowed standard code to be entered into the control's NotInList event procedure.
In the table designs I've changed the DisplayControl property of the foreign key Location columns in the tables to Text Box. Combo boxes should only be used in forms. As users should never interface with the data directly in tables' raw datasheets using a combo box in tables serves no purpose.
Thanks a million Ken, as well as SMarshall and Scottgem. I appreciate all of you guys taking the time to help me. While I ultimately resolved the issue by letting Ken edit my database directly, I still learned a lot and will keep playing with it. Next up is figuring out how to do the Sold/Not Sold feature. Of course I'll make frequent backups! LOL!
Thanks again!