jQuery Grid Plugin - jqGrid

Hello guys, this is my first post in this forum, so please, be pacient with me.

I need to set my summary to show the sum of all rows in my grid, even the rows that are inside other pages.

The absolute sum of values.

I was searching for it, and i saw a lot of people with this problem, so i don't think it is a problem with my code. 

Sounds more like a design in the grouping mecanism it self. Or not, i don't know.

But, to be clear, i think i need to make a call to server side to get the sum from there, is this possible? if so, how should i do it with json?

I was thinking about use the formatter option, but then it is trigered line by line, and i don't think this is the idea becouse the sum will come entire in the first call.

So, any suggestions? 

Thanks !!!