Access Formula values at runtime

How can i retrive value of a formula field or any other field in code at runtime, which can be used in code 4r further operations.

e.g :I have a formula field which calculates a Value Discrepancy.I have to show a message box Message Box based on its value from the code.
I am using CR for VS2005


Thankyou
ShauryaFinally i found the solution to my problem so i am sharing the solution here.

The values that are printed on the report can be accessed from the code by this code.

CrystalDecisions.CrystalReports.Engine.ReportDocument a = new CrystalDecisions.CrystalReports.Engine.ReportDocument();

string value=a.Rows[0][20].ToString();

The Rows property contains the data on the front page of the report.|||how did you get this CrystalDecisions.

Any reference to add to repor to get it.

Amarjit