i have product with category for example 

Product One Product Two & Product Three 

Product One and Product Two under Category one 

and Product Three Under Category Two 

i want to present product in sale order print report 

group with Category with Sub total ....show in report

Category A

-------------------Product A 100
....................Product B 200

--------------------------------------Sub------300

Category B
...................Product C 500
..................Product E 100
-------------------------------------Sub----------600
---------------------------------------Grand-----900

any coding hint please