Benchmarking Performance Sales Goal on Running Sales Widget

Good Morning!  We're just getting into Analytics and are starting with a Performance Sales-focused dashboard.  One of the widgets we'd like is a running sales with a benchmark/horizontal line indicating the budget for the performance so we can get a quick visual of performance sales to goal.  I have achieved the the running total sales, but can't get the budget value to appear.  I'm using a line chart and when I add the budget as second value it won't add.  I was thinking the budget value could be put on a second y axis.  Am I going about this wrong?  Is there a better way to do this?  Thanks in advance for any ideas.