Counting Users logged into Access DataBase in Delphi

Hi. I have converted some BDE files (Paradox) into an Access MDB and I used to have a procedure which counted the number of users logged into an application
by cloning cursors and using the BDE function "Check(DbiIsRecordLocked(Table.Handle, Locked))". This always worked great when users logged in and out, even if users crashed their OS.
I have searched about and came up with the code from Microsoft which uses OpenSchema with a SchemID which seems to not work (which I modified below).
I also checked some code which reads the LDB file, which I also have problems with as it is difficult to read this file, and anyway I dont feel its safe.

Anyone done this in Delphi already?

My test is like this so far (trying to load details into a memo), I guess I must not be understanding something :-))
I have 4 objects on a form: ADOconnection, ADOTable and a Tmemo and a Tbutton...

procedure TForm1.Button1Click(Sender: TObject);
const  SchemaID=  '{947bb102-5d43-11d1-bdbf-00c04fb92675}';
  var  Schema: TSchemaInfo;  Restrictions: OleVariant;
begin
  Schema:= siProviderSpecific;
  Restrictions:= 0; // not sure about this?
try  with ADOConn do begin
       Connected:= True;
       OpenSchema(Schema, Restrictions, SchemaID, TADODataSet(tblADO)); //crashes here so must be wrong
     end;
     with tblADO do begin
       First;
       while not EOF do begin
         AMemo.Lines.Add(Fields[0].Name);
         AMemo.Lines.Add(Fields[0].Value);
         Next;
       end;
    end;
except on e:exception do showmessage(e.message); end;
end;