Not sure, but it all depends on the receiving field data-type.
aa = Me.D1AM + vbNewLine & DLookup("[Given]", "Volunteers", "[ID] = " & Me.Combo14)
This seems to be passing a STRING value.
I'd use:
aa = Me.D1AM & vbCRLF & "'" & DLookup("[Given]", "Volunteers", "[ID] = " & Me.Combo14) & "'"...