procedure TMainForm.Edit1Change(Sender: TObject);
begin
  if length(Edit1.Text) > 0 then
  begin
    Table1.Filtered := TRUE;
    UpdateFilter(Table1);
  end
  else
    Table1.Filtered := FALSE;
end;

procedure TMainForm.UpdateFilter(DataSet: TDataSet);
var
  FR: TFilterRecordEvent;
begin
  with DataSet do
  begin
    FR := OnFilterRecord;
    if Assigned(FR) and Active then
    begin
      DisableControls;
      try
        OnFilterRecord := nil;
        OnFilterRecord := FR;
      finally
        EnableControls;
      end;
    end;
  end;
end;