I've tried both ways but to no avail. I've set up an Open rule to query both the SharePoint List and the Vendor List. Then I have a drop-down list that populates with all the POs in the Sharepoint list (Called FileName in the Check Request form). So, what I want to do is, depending on what PO is selected in that drop-down, populate the Client ID, Client Address, Client City, etc. among other fields that are promoted in the SharePoint List. On the PO drop-down box, I've got it set right to pull the list box entries. I created a dummy field (VenName) that eventually won't show and I pulled in a value based on the selection in the drop-down box. Then I opened properties for the PO drop-down, and set a Rule to set the VenName as the current value selected in the PO drop-down. (and that populates just fine). But if I change that to make it pull in the actual Vendor Name, it returns a blank field....no error.
My coding experience and knowledge is very limited, so I'm either not considering some kind of logic, or I'm looking at this too deeply. :)