Get Value from Current Row

It’s a little convoluted, but I have a table (vendors) attached to a master model (rfq).  Inside the vendors table there are drawers which include another table (dims) directly connected to each vendor.  When the user adds a record to the dims model, I need the Name field to be equal to a field (VendorID) from the vendor model.  Since the user may add multiple dims to multiple vendors, I can’t just assign the VendorID from the top record of the vendor table.  I tried, {{VendorID__c}}, but it isn’t working…  The action sequence is initiated at the “Add new row” action in the dims model.  Any thoughts?