private void MoveRow(int rowa, int rowb)
{
string start = listStore.GetValue(rowa, startCol);
string end = listStore.GetValue(rowa, endCol);
listStore.SetValue(rowa, startCol, listStore.GetValue(rowb, startCol));
listStore.SetValue(rowa, endCol, listStore.GetValue(rowb, endCol));
listStore.SetValue(rowb, startCol, start);
listStore.SetValue(rowb, endCol, end);
}