type
  TDBType = (dbtSQLServer, dbtMDB, dbDBF);
  public
    function ConnectDB(const FileName : TFileName; const DBType : TDBType; pwd : string = ''):boolean;
bla bla.........
function TDM.ConnectDB(const FileName: TFileName; const DBType : TDBType; pwd : string = ''): boolean;
var
  DBName : widestring;
  SQLConnection : TSQLConnection;
begin
  Result := False;
  if DBType = dbtMDB then
   begin
    AdoConn.ConnectionString:='Provider=Microsoft.Jet.OLEDB.4.0;Data Source=' + FileName + ';Persist Security Info=False';
    if pwd <> '' then AdoConn.ConnectionString:=AdoConn.ConnectionString + ';Jet OLEDB:Database Password=' + pwd;
    DBName := FileName;
  end;
  AdoConn.LoginPrompt := False;
  result:=True;
  MainForm.ConnectedTO := DBName;
  try
    if NOT AdoConn.Connected then AdoConn.Open;
    Result:=True;
  except
    ON E:Exception do
    begin
      MessageDlg(e.Message,mtError, [mbOK],0);
      MainForm.ConnectedTO := '';
      pwd := InputBox('MDB with password','If this is password protected, please enter password (leave empty to cancel):','');
      if pwd = '' then
      begin
        Result := false;
        Exit;
      end
      else
        if ConnectDB(FileName, DBType, pwd) then Result := True;
    end;
  end;
end; (ConnectDB )