Importing to an unrelated table??

Scenario: Invoices and LineItems.

I want to collect batches of Invoices into an archive. I created Archive_Invoices and Archive_LineItems by simply duplicating Invoices and LineItems, and then changing all data types to Text in the archived versions. I then scripted the archiving as follows:

Go To Layout(archive_invoices)

Import(DBFile.fp7, Update Matching) /* import from Invoices */

Go To Layout(archive_lineitems)

Import(DBFile.fp7, Update Matching) /* import from LineItems */

Specifying the import order for the first import was easy. Source was Invoices, target was Archive_Invoices. Significantly, "Archive_Invoices" was listed in the Target pull-down menu as a related table.

It was setting up the LineItems import where I had trouble. I thought it was a completely parallel situation, but Archive_LineItems was listed in the Target pull-down menu as an UNrelated table. And "update matching records" and "add remaining records as new" were grayed out.

What gives? Invoices and Archive_Invoices aren't related any more than LineItems and Archive_LineItems are, and I fail to see why relatedness matters at all when importing or exporting. But since it apparently does, why does FM believe that Invs and Archives_Invs are related, while LIs and Archive_LIs aren't??

Thanks,

Chap