the following example is applicable to both Basic and Crystal syntax: 
Suppose that you can choose one of two offers: $20,000 now or guaranteed payments of $5,000 after 1 year, $10,000 after 2 years and $15,000 crystal scheduler after 3 years. What is the better offer? One way to quantify this is to calculate the internal rate of return. If you take the second offer, you can't take the first so that is like experiencing an initial payment of $20,000 followed by the receipts:
Rem Basic syntax
formula = IRR ( Array(-20000, 5000, 10000, 15000))
//Crystal syntax
IRR ([-20000, 5000, 10000, 15000])
Returns 0.194 (rounded to 3 decimals) or 19.4 percent interest. So all other things being equal, if you think that 19.4 percent is a good rate of Crystal Reports Bursting return, you would prefer the second offer. 
There is no direct formula for the IRR function and so Crystal Reports calculates the value by iteration. The process depends on the initial guess for the internal rate of return. If the program reports an error, try changing the value of the guess argument to be closer to what you expect the internal rate bursting crystal reports of return should be.
https://in.answers.yahoo.com/question/index?qid=20081222223351AANdKEv
