Add Dynamic reference lines to scatter plot

While using the scatter plot, I need to be able to add a dynamic reference line using a measure. Currently the only reference lines you can add to a scatter plot are constant lines.

An example is if you are using a scatter plot to track multiple businesses performance throughout the month (x and Y axis measures reflect different % complete sales measures). In theory, 25% through the month you should have achieved 25% of your goal. I want to be able to draw a line (on X and Y axis) that clearly identifies the 25% goal.