How To Do Advanced Sum?

Hi

I'm new in Reporting Services and I have a task to solve. I wonder how to do it in Reporting Services.

For example I have few records:





ID
Year
Q1
Q2
Q3
Q4

1
2005
0
0
10
20

2
2006
20
20
35
35

3
2007
40
45
45
10 Now I create two parameters:
Q and Year

When I run this report I want to choose for example Year = 2006, and Q = 3

When I choose these values I need to calculate a field in report like this:

needed_sum = 0(Q1,year=2005) + 0(Q2,year=2005) + 10(Q3,year=2005) + 20(Q4,year=2005) + 20(Q1,year=2006) + 20(Q2,year=2006) + 35(Q3,year=2006)


I need to declare variables, like it is calculating on a section in other reports systems. Here I found only code for report where I can write some functions.

Anyway..
Did someone knows how to solve this problematic task??

Regards

Bashay