Foreach loop on datatable on same column

Question

Hi, I want to add a row at a specific location. I have a table with following data

 

InvID	CatID	ItemCode	BatchNo	Price	Qty	Total
2	122	43	DFR-43	33$	3	99$
2	643	76	SGR-3	25$	2	50$
2	643	12	KLS-E3	45$	2	90$
2	177	65	EWQ-22	8$	1	8$
2	177	988	FDS-32	11$	7	77$
2	177	45	VFE-44	22$	4	88$
2	355	19	DRG-28	15$	3	45$
2	355	39	CSX-099	6$	2	12$
2	355	26	XDE-134	13$	8	104$
2	355	87	VVF-2002	56$	5	280$
2	355	59	BNM-344	34$	2	68$
2	165	374	SDE-3	20$	2	40$

I want to add a row after ending each catID for showing the sum of that Category.

likewise i want to add a row at second last postion as
Total : 509$

 

need urgent help... 

Thanks