I guess I've come up with a good solution:
After filling the DataTable, you add a bool column manually:
// [...]
daOleDb.Fill(dtResult);
DataColumn dtCol = new DataColumn("Bool", typeof(Boolean));
dtCol.DefaultValue = false;
dtResult.Columns.Add(dtCol);
dtCol.SetOrdinal(0);
DataGrid1.ItemsSource = dtResult.DefaultView;
This will not affect the "RowsChanged" event and as it's an added column, before doing
daOleDb.Update(dtResult);
you can simply delete/remove it again (shouldn't make any difference as added columns do not affect any ChangesEvent when being deleted either)
dtResult.Columns[0].Remove(); // or Columns.Delete(...)