Vendor Lookup in Dexterity

Spent the better part of this day on this one so here's hoping you don't have the same.

I was trying to add a vendor lookup to my custom Dexterity window.  Using the traditional script of "open window ... return to" and "run redisplay button" was getting me nowhere.  The vendor lookup window opened but there were no vendors in the scrolling window.

The win in this was to set the sort option on the window.  Here is my code that worked.

open form Vendor_Lookup return to 'Vendor ID';
'Vendor ID' of window Vendor_Lookup of form Vendor_Lookup = 'Vendor ID';
'Vendor Sort By' of window Vendor_Lookup of form Vendor_Lookup = 1;
run script 'Redisplay Button' of window Vendor_Lookup of form Vendor_Lookup;
Bottom line is if you're trying to open an existing GP lookup and getting no data try to set the "Sort By" field.