Views relation problem -- item in a group

I have a series of CCK content types. An "Agency" issues "Call for Tender"s; a "Vendor" can submit a "Bid" if that Vendor is approved by that Agency. A User with the Vendor role is associated with one Vendor, while the Vendor-Agency relation is many-to-many.
I want to list the Tenders a User may Bid on.
I can start with the logged-in User. One relation gets me the Vendor; the next gets the Agencies who have approved the Vendor; and the last gets the Bids from those Agencies. It's a little round-about, but the logic seems straightforward.

The problem is that the Vendor record has the VendorUsers inside a group ("group_vendor_users"), since there is an indeterminate number of them.
But that means that the Vendor-User relation is in a "content_field_vendor_users" table:

CREATE TABLE `content_field_vendor_users` (
`vid` int(10) unsigned NOT NULL default '0', 
`nid` int(10) unsigned NOT NULL default '0', 
`delta` int(10) unsigned NOT NULL default '0', 
`field_vendor_users_uid` int(10) unsigned default NULL, 
PRIMARY KEY  (`vid`,`delta`), 
KEY `nid` (`nid`) );

So I need to relate to content_field_vendor_users.nid or content_field_vendor_users.nid to reference the User's Vendor. Views won't go there, and I have been unsuccessful hacking a $view/$handler to reference it either. (My closest so far errors "Field handler content_field_vendor_users.vid is not available.")

Does anyone have a suggestion, workaround, hack or interesting idea?

(( This supercedes need to use content_field_foo.vid in a relation. ))