@Override
    public void setValueAt(Object aValue, int rowIndex, int columnIndex) {
      if (rowIndex >= myVariables.size()) {
        return;
      }
      final Variable variable = myVariables.get(rowIndex);
      if (columnIndex == 0) {
        variable.setName((String)aValue);
      }
      else {
        variable.setExpression(((Expression)aValue).getExpression());
      }
      fireTableDataChanged();
    }
@Override
    public void setValueAt(Object aValue, int rowIndex, int columnIndex)