Then just build a temporary table that holds ALL the names in a single field, along with an address:
Currentdb.Execute "Select Address, csz INTO YourTempTable FROM Select Distinct Address, csz FROM YourExistingTable"
Now add a SendTo field:
Currentdb.Execute "ALTER TABLE YourTempTable ADD COLUMN SendTo TEXT(255)"
Now build a recordset where you can loop through all names for a specific Address + csz, and concatenate the names:
Dim rst As DAO.Recordset
Dim rstNames as DAO.Recordset
Dim sNames as String
set rst = Currentdb.OpenRecordset("SELECT * FROM YourTempTable")
Do Until rst.EOF
Set rstNames = Currentdb.Openrecordset("SELECT * FROM YourExistingTable WHERE [Address]='" & rst("Address") & "' AND csz='" & rst("csz") & "')"
sNames = ""
Do until rstNames.EOF
sNames = sNames & vbCrLf & rstNames("First_Name") & " " & rstNames("Last_Name")
rstNames.movenext
Loop
rst.Edit
rst("SendTo") = sNames
rst.Update
Loop