read the changed value from "Workbook_SheetCalculate(object sh)" function for Excel

Question

Hi, I've written the WorkbookEvents_SheetCalculateEventHandler event to trigger for recalculation in Excel in C#.net2.0

public event Excel.WorkbookEvents_SheetCalculateEventHandler SheetCalculate;
SheetCalculate = new Excel.WorkbookEvents_SheetCalculateEventHandler( ThisWorkbook_SheetCalculate);

The function Workbook_SheetCalculate(object Sh) triggers when there is a formula change in the excel sheet.
My aim is to read the function result from the Sh object.

for example, if A1=15, A2=17 and A3=SUM(A1,A2).Now I change the  A1=17 so now I  A3 value also changed because we write function for that.I want Capture that A3 Value also.

Workbook_SheetCalculate fires as soon as there is change in A1 or A2. I need to read the function result. Please guide me to get the value off A3.
Thanks in advance.