Can you just create calculated fields for each District's sales? Like:
IF[Store]='A' THEN [Sales]
elseif [Store]='B' THEN [Sales]
elseif [Store]='C'THEN [Sales]
elseif [Store]='D'THEN [Sales]
There are certainly other options, including re-shaping your data to include the districts. This is just one way to get at the numbers, but it may be limiting, depending on what you need to do with the numbers. Someone may chime in with a better solution. I was able to get your numbers in the attached, though.
District A & B Sales.twbx.zip 11.4 KB
Thank you for the answer Matthew.
Sorry, I forgot to mention that [Sales] is acutally a calcuated field measure which is =sum([something])/sum([something]). Is that why I get a message sayting that "Cannot mix aggregate and non-aggregate comparasions or results in 'if' expressions" when I tried your solution?
Quick answer: yes. I am away from my machine for the evening some hopefully someone else can chime in with a solution or explanation. If not, I'll take another look tomorrow.