Category talk:Report development

I want to know if there is a way to get sum values from a report, i mean, it is very usefull to use sum fields in reports but i can not get value from a sum field, for example, i have 3 fields from a table, 2 reals and 1 percent, i can sum real values but sum percent value would be an error, i need to get value from sum fields in order to calculate percent, how can i do this? (now i'm using variables but it would be easy to find another way to do it)