>I have an SSRS report with a table that shows two numeric columns and the difference between them
>I'm using the report builder that comes with VS 2013. It's a local report associated with a Winform app.
>I wanted to sum the differences and couldn't see a straightforward way to sum an expression.
>
>I found some convoluted solutions on the web but decided instead to add a computed column to the dataset and used that.
>
>Is there a better way?


There are multiple ways - another way is to use the ReportItems! Collection. So if you had 2 textboxes in the total summary area (called txtTotal1 and txtTotal2), you could have a third textbox with the expression.....

ReportItems!txtTotal1.Value - ReportItems!txtTotal2.Value

(assuming I'm understanding your question correctly)