AbstractCalculationMonitor class

Monitor for user to track the progress of formula calculation.

The AbstractCalculationMonitor type exposes the following members:

Property	Description
original_value	Gets the old value of the calculated cell. Should be used only in `AbstractCalculationMonitor.before_calculate` and `AbstractCalculationMonitor.after_calculate`.
value_changed	Whether the cell’s value has been changed after the calculation. Should be used only in `AbstractCalculationMonitor.after_calculate`.
calculated_value	Gets the newly calculated value of the cell. Should be used only in `AbstractCalculationMonitor.after_calculate`.

Method	Description
before_calculate	Implement this method to do business before calculating one cell.
after_calculate	Implement this method to do business after one cell has been calculated.
on_circular	Implement this method to do business when calculating formulas with circular references.