Calculate percent of row in a table

Hello,

I have a large matrix set up and would like to set up a measure that calculates the total row percentage. ie:

Item   Qtr1   Qtr2   Qtr3   Qtr4   Total

A        100    300     200    400     1000

The measure would calculate as 

Item   Qtr1   Qtr2   Qtr3   Qtr4   Total

A        10%    30%   20%   40%    100%

I also have a handful of page level filters that I have to account for. I tried 

%ofTotal = DIVIDE(SUM(Table[Sales]),CALCULATE(SUM(Table[Sales]), ALLEXCEPT(Table,Table[Sales]

This returns a percentage of total sales for the entire table. Please help.