how to dynamically create summary in crystal reports using c#

See more:

C#

hi i am yogesh and i have created a dynamic crystal report in which users can get any number of columns(and in any order) according to their need.
Eg:- i have 5 check boxes------
1.code.
2.name.
3.date.
4.pcs.
5.amount
Here user will get the desired fields in any order in crystal report.
Eg:- if user selects 2nd,4th,and 5th checkboxes, fields are shown in proper order starting from 1 as below.
(1-name,2-pcs,3-amount)
But my problem is that i need to display summary of amount, which user can select at
any position. so i need to display summary of particular column dynamically..
Please help if somebody knows the answer.... how to create summary of a column dynamically....