Can i change crystal report values on loading of report

Question

Hi friends
i have a doubt
This is my Crystal report

name	class id	attid
ram	1	13
krish	1	-13
abcd	1	12

now what i want is on crystal report load i have to get the report as if attid >0 i have to get result as 0 else 1
is it possible? Please help me
am getting attid from database. How can i change these values on loading of report? please help me.

Thanks
Znaneswar