list and matrix grouping

hi i would to get some help from you guys. i am doing an item catalog,
basically the page will be full of pic and descriptions. i have done the
horizontal part like 3 pic and their descriptions in a row by using matrix
and list. my problem is, how can i display the header of each catagory just
once for each catagory. Currently my sr display each row has a header. i
would like to have each header display just once before go to second
catagory. Please advice.
Current Result:
---
Battery Battery Battery
<-- Header
---
pic description pic description pic description <-- pic
and description
---
Battery Battery Battery
<-- Header
---
pic description pic description pic description <-- pic
and description
---
Charger Charger Chareger <--
Header
---
pic description pic description pic description <-- pic
and description
Idea Result:
----
Battery
<-- Header
----
pic description pic description pic description <-- pic
and description
pic description pic description pic description <-- pic
and description
pic description pic description pic description <-- pic
and description
----
Charger
<-- Header
----
pic description pic description pic description <-- pic
and description
pic description pic description pic description <-- pic
and description
pic description pic description pic description <-- pic
and description
Thankssorry~ the current and idea result should be like this.
Current Result:
---
Battery Battery Battery <-- Header
---
pic+detail pic+detail pic+detail <-- pic and detail
---
Battery Charger Charger <-- Header
---
pic+detail pic+detail pic+detail <-- pic and detail
---
Headset Carrying Battery <-- Header
---
pic+detail pic+detail pic+detail <-- pic and detail
Idea Result:
---
Battery <-- Header
---
pic+detail pic+detail pic+detail <-- pic and detail
pic+detail pic+detail <-- pic and detail
---
Charger <-- Header
---
pic+detail pic+detail <-- pic and detail
---
Headset <-- Header
---
pic+detail <-- pic and detail
---
Carrying <-- Header
---
pic+detail <-- pic and detail|||actually not the header issue, i just want to group all the item together
under the same catagory and display 3 item in each row.
i tried add two expression into list1_Details_Group expression which do the
category grouping first before 3 row group into one group.
1. =Fields!category.Value
2. =Ceiling(RowNumber(nothing)/3)
however my result become like this.
--
|item 1 - category 1| <- row 1
--
|item 2 - category 1| <- row 1
--
|item 3 - category 1| <- row 1
--
|item 4 - category 1| <- row 2
--
|item 5 - category 2| <- row 3
--
|item 6 - category 2| <- row 3
--
|item 7 - category 2| <- row 4 <-- problem here
--
|item 8 - category 2| <- row 4
--
|item 9 - category 2| <- row 4
--
idea resule:
--
|item 1 - category 1| <- row 1
--
|item 2 - category 1| <- row 1
--
|item 3 - category 1| <- row 1
--
|item 4 - category 1| <- row 2
--
|item 5 - category 2| <- row 3
--
|item 6 - category 2| <- row 3
--
|item 7 - category 2| <- row 3
--
|item 8 - category 2| <- row 4
--
|item 9 - category 2| <- row 4
--