jQuery Grid Plugin - jqGrid

Hi, I´am working with treeGrid and i have different levels, is there a way to sum this levels?

Something like that:

--level0 -----------   78.00 (i need total of levels1)

         ---level1 ---   37.00  (i need de total of childs here!!!)

             ---level2 - 10.00

             ---level2 - 12.00

             ---level2 - 15.00

         ---level1 ----  41.00 (i need de total of childs here!!!)

             ---level2 - 20.00

             ---level2 - 20.00

             ---level2 - 1.00

I´ve read some about method "getNodeChild" but i don´t know how to use it.

Some body have an example??

thanks.

EAR