var
  i: Integer;
  fName: string;

............
{ Определение изменения месторасположения колонок }
............

with DBGrid1.DataSource.DataSet as TTable do
  for i := 0 to IndexDefs.Count - 1 do
  begin
    fName := DBGrid1.Fields[0].FieldName;
    if Copy(IndexDefs[i].Fields, 1, Length(fName)) = fName then
      IndexName := IndexDefs[i].Name
  end;