I have an SSRS report with several computation.
I have done already the dataset and I already  have the ssrs report template with corresponding fields using dataset.lateron the users wanted to have a computation on the report.  My question is how to do this computation in SSRS. Do I need to make variable in expression? Need your input guys.

resultset: 
ItemID—1—2—-3--4---TOTAL1 --A1—A2—A3—A4—B1—B2—B3—B4—TOTAL2
11111--9-6--4--5-----24------5-3--2---2-4--3--2--3--24

These are the requirements.:
1.	The number (1) column is the total of A1 and B1
2.	The number(2) column is the total of A2 and B2
3.	(3) column is the total of A3 and B3
4.	(4) column is the total of A4 and B4
5.	TOTAL1 is the total summary of column 1 to 4
6.	TOTAL2 is the total summary of A1 up to B4


I tried this in my expression
Do i need this to place in variable?

for column 1
=Sum(Field!A1.Value)+Sum(Field!B1.Value) up to D1
for column 2
=Sum(Field!A2.Value)+Sum(Field!B2.Value)  up to D2
and so on...

For the TOTAL1 ??
=Sum(Field!1.Value)+Sum(Field!2.Value)+Sum(Field!3.Value)+Sum(Field!4.Value)