How to disable Row label from the aggregation function in Pivot table

Question

Hello everyone,
I have table in Power Pivot like shown below:
Item_Name
Category
Vendor
Sales_Amount
Item 1
Category 1
Vendor 1
30
Item 2
Category 1
Vendor 2
25
Item 3
Category 2
Vendor 3
50
Item 3
Category 2
Vendor 3
60
Item 3
Category 2
Vendor 3
20
Item 2
Category 1
Vendor 2
10
Item 2
Category 1
Vendor 2
30
Item 2
Category 1
Vendor 2
100
Item 2
Category 1
Vendor 1
20
By using above table i have to create Rank(Based on Sales amount) by Category and Item name in Pivot table, i have done easily like added two dimension attribute(Category, Item_Name) into row label and Sales_Amount into aggregation tab then I calculated
rank:=RANKX(ALL(Sales[Item_Name]),[Sum of Sales_Amount]) so finally pivot table looks like shown below:
But end user want to see the vendor name also in the pivot table but the Rank suppose to be based on Sales amount by Category and Item name. if i added the vendor name also into the row label, rank calculated based on on Sales amount by Category, Item
name and vendor.
I would be really grateful if anyone advise how to fix this problem as it will be helpful my most of the reports.
Regards,
Robert 

Answer 1

Darren Gosbell,
Thanks for your reply.
Item_Name
Category
Vendor
Sales_Amount
Item 1
Category 1
Vendor 1
30
Item 2
Category 1
Vendor 2
25
Item 3
Category 2
Vendor 3
50
Item 3
Category 2
Vendor 3
60
Item 3
Category 2
Vendor 3
20
Item 2
Category 1
Vendor 2
10
Item 2
Category 1
Vendor 2
30
Item 2
Category 1
Vendor 2
100
Item 2
Category 1
Vendor 2
20
Item 4
Category 1
Vendor 2
3
Item 4
Category 1
Vendor 2
50
Item 4
Category 1
Vendor 2
3
The above is my new source data.
I used this function to calculate  Rank:=RANKX(ALL(Sales[Item_Name]),[Sum of Sales_Amount])
and also used yours below:  
Rank2:=RANKX(SUMMARIZE(ALL(Sales),[Item_Name],[Category]),CALCULATE([Sum of Sales_Amount],ALLEXCEPT(Sales,Sales[Item_Name],Sales[Category])))
The Preceding screenshot is the result of our two function but i wanna pivot table like shown below:
Could please help me to fix it out.