{
 In the "Object Inspector" set your DBGrid's Option for dgMultiSelect = True.
 The Grid_Edit function calls for each selected DBGrid-Row a data-processing
 function.
 Return value is the number of processed rows.
}
function TForm1.Grid_Edit(dbgIn: TDBGrid; qryIn: TQuery): Longint;
 // declared in the private section
begin
 Result := 0;
 with dbgIn.DataSource.DataSet do
 begin
  First;
  DisableControls;
  try
  while not EOF do
  begin
  if (dbgIn.SelectedRows.CurrentRowSelected = True) then
  begin
  { +++ Call here the data-processing function +++
  }
  Inc(Result);
  end;
  ;
  end;
  finally
  EnableControls;
  end;
 end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
 Form1.Caption := 'Processed: ' + IntToStr(Grid_Edit(DBGrid1, Query1));
end;