So - when I changed the filter to select the Vendor field in the main DS, InfoPath used the absolute path to the vendor - which would not have helped the situation at all. :) Instead, I manually changed it to use the current() function. Since the rule is on the Vendor node, which is in a repeating group, current() will always return whatever instance of the Vendor you just set the value on. Give this copy a try - right click the link in the heading of this post and save the file locally. Right click the saved file and select "design" - then you can preview and test it out.
Hilary Stoupa
