[AccessD] Set Recordsource of sub Form

Dear List:
 
I can't seem to get the syntax on this right.  From a main form I want to
set the recordsource of a sub form.  I'm trying:
 
    Me.ClientPersonsSubFrm.RecordSource = strRecordSource & " AND
MailingList = True " & strOrderBy

but it won't compile - says 'Method of Datamember no found'.
 
What is the correct syntax to set the record source on a sub-form?
 
MTIA
 
Rocky