[AccessD] Nz Joining fields

Awhile back someone sent out how to join 2 fields with an Enter in between
the fields and if one field was Null, it would not show the Enter. I
remember it used the Nz.

I need to concatenate Requestor & Customer. If there isn't a requestor name
it will show the customer only, but on the first line.

Requestor Name
Customer Name

This doesn't work:
CusReq: [dbo_customers].[firstname] & " " & [dbo_customers].[lastname] &
Left(Chr(13) & Chr(10),Len(Nz([dbo_customers].[firstname] & " " &
[dbo_customers].[lastname]))*Len(Nz([dbo_Requestors.FName &" "&
dbo_Requestors.LName]))) & [dbo_Requestors.FName &" "& dbo_Requestors.LName]