I copied the following into my new module (although I have no clue what it
means). When I ran Compile, I got the error message: "User defined Type not
defined" and
the "rs As New ADODB.Recordset" in the 2nd line of the commented in section
was highlighted (not in yellow but in blue as if I was about to copy that
section).

Incidentally I checked the appropriate Microsoft DAO x.x Object Library as
you suggested.

Any idea as to what's wrong?

Thanks again.

Function Concatenate(pstrSQL As String, _
       Optional pstrDelim As String = ", ") _
       As String
'Created by Duane Hookom, 2003
'this code may be included in any application/mdb providing
'   this statement is left intact
'example
'tblFamily with FamID as numeric primary key
'tblFamMem with FamID, FirstName, DOB,...
'return a comma separated list of FirstNames
'for a FamID
' John, Mary, Susan
'in a Query
'SELECT FamID,
'Concatenate("SELECT FirstName FROM tblFamMem
' WHERE FamID =" & [FamID]) as FirstNames
'FROM tblFamily
'

'======For DAO uncomment next 4 lines=======
'====== comment out ADO below =======
   'Dim db As DAO.Database
   'Dim rs As DAO.Recordset
   'Set db = CurrentDb
   'Set rs = db.OpenRecordset(pstrSQL)

'======For ADO uncomment next two lines=====
'====== comment out DAO above ======
   Dim rs As New ADODB.Recordset
   rs.Open pstrSQL, CurrentProject.Connection, _
   adOpenKeyset, adLockOptimistic
   Dim strConcat As String 'build return string
   With rs
       If Not .EOF Then
           .MoveFirst
           Do While Not .EOF
               strConcat = strConcat & _
               .Fields(0) & pstrDelim
               .MoveNext
           Loop
       End If
       .Close
   End With
   Set rs = Nothing
'====== uncomment next line for DAO ========
   'Set db = Nothing
   If Len(strConcat) > 0 Then
       strConcat = Left(strConcat, _
       Len(strConcat) - Len(pstrDelim))
   End If
   Concatenate = strConcat
End Function