Add Target Line To Pivot Chart

Hello,

I'm really really stuck on a frustrating issue and can not seem to find a solution. Any help would be greatly appreciated! What I want to do seems simple but I just can't get it to work. I'm trying to create a pivot graph with a target line set at "50" across the entire graph. It has to be a pivot graph because the data will change often and needs to be manipulated by people who are less familiar with Excel than myself.

I attached an example but you will see that my target is not displayed as a horizontal line but instead it's simply just another bar.

Thank you in advance to anyone that can assist me!

- Justin