Many thanks for your suggestion.  The second suggestion (turn off warnings) does not seem to work.  The message I get is a Microsoft Visual Basic message run-time error '3022'  The changes you requested to the table  were not successful because they would create duplicate values in the ... primary key ..
I used DoCmd.SetWarnings (False) before the Update of the record set and back again to true afterwards

---

Reply from Richard Rost:

Hmmm... in that case, you'll have to check each record as you add it with a DLOOKUP statement to see if it's there. If the DLOOKUP returns NULL then you can add it.