RDLC Report based on column criteria

Item_Code	Category_ID	Category_Name	Closing_Stock_Qty	Stock_Age
1246060	12	Children shoes	20	2
1246061	12	Children shoes	25	5
1246062	12	Children shoes	60	2
4246060	14	School books	50	6
4246061	14	School books	20	2
4246062	14	School books	50	2
5246060	15	Mobile phones	25	2
5246062	15	Mobile phones	60	5
5246061	15	Mobile phones	30	2

I have the table shown above. I want to make an RDLC report which can filter the above table and

Produce the report based on the stock_ age. That is I want to have a summary report based on the stock_age and grouped by category_name . For example I want to filter according to stock_age =2

and get the following report:

Category_Name	Closing_Stock_Qty	Stock_Age
Children shoes	80	2
School books	70	2
Mobile phones	55	2

I have tried to use

=Sum(IIF(Fields!Stock_Age.Value=1,Fields!Closing_Stock_Qty.Value,0))

Kindly assist me to sort out this issue since Iam new to C# rdcl reports.