>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?

You could also sum differences this way...

SUM( Fields!Value1.Value) - SUM( Fields!Value2.Value)