Thanks, I did try this but was receiving errors. This was the syntax I was using in the DTL:

..Piece(source.{AlternateVisitID().ID},"~",,*)

This is the full PV1 segment:

PV1|1|O|NPID15T^MEDIFREN^^^^^^^NURSE LED "TB" TELEPHONE CLINIC|||||||||||||||1|015728690002||||||||||||||||||||||||||20210203114600|||||15081942~15081951~15108961~15280550

Thanks for the help Enrico. It's working perfectly now.

Martin