Creating a One to Many relationship with UDTs and UDFs

SUGGESTED

I am trying to add a UDF with a one to many relationship with an inventory item.

I created a UDT to store the values of the UDF that will be associated with the items.  Then I created a second UDT to store the relationship between the items and the UDF.   The first field that holds the valid values from the first UDT was added and I was able to validate from the Validate tab to the UDF.  Then I try to add the second field to hold the inventory item and no matter what I do I can't get the tbe 3.Data Sources to be available.

I can see the Data Sources tab on a system defined table like CI_Item or SO_Sales Order Header.  Is this a limit on UDT's in Standard or Advanced (Providex)?