It's hard to say since "two tables away" is a big vague.
You appear to have these relaitonships:
PurchaseOrders::__pkPurchaseOrderID = LineItems::_fkPurchaseOrderID
Product::__pkProductID = LIneItems::_fkProductID
Suppliers::__pkSupplierID = _fkSupplierID
and as you have discovered that won't work for your conditional value list. But you can make new Tutorial: What are Table Occurrences? of Products and Suppliers and add them in to the above relationships to get a conditional value list:
PurchaseOrders::_fkSupplierID = POSupplier::__pkSupplierID
POSupplier::__pkSupplierID = POProducts::_fkSupplierID
Then you can set up your value list to list products from POProducts, include only related values starting from PurchaseOrders.
Thanks for being quick! You understood correctly! I've been trying hard in different ways (including yours) and it didn't work...Now it does...I must have done something wrong..
Thanks a lot once again!