New Record from Combo Help

[pfm721]

I have a set of cascading combos. The first one in the list is programmed to
open a form to add a Vendor if the user selects <NEW>

SELECT tblVendor.VendorName FROM tblVendor UNION select "<NEW>" from tblVendor
ORDER BY tblVendor.VendorName;

The next combo is cboDoctor and I would like it to have similar
functionality. Currently to make the cascading combos work it looks like this

SELECT tblDoctor.DoctorName, tblVendor.VendorName, tblDoctor.VendorName
FROM tblVendor LEFT JOIN tblDoctor ON tblVendor.VendorName =
tblDoctor.VendorName
WHERE
(((tblVendor.VendorName)=[Forms]![Form1]![frmInfoSub].[FORM]![Location]));

Any suggestions? It doesn't have to work the exact same way as the Vendor
one, just something similar so the user can add a new doctor.