SOLVED-Dynamically change size/range of x axis of chart

Howdy !

My first post on here, so let me know in the comments if I left anything out.

I have attached a simplified version of my project which illustrates my problem of creating a chart, when the data dynamically changes quantity, the graph gets thrown off.

You can see that if you change the subject in the drop down menu, the graph gets messed up because each subject has a different duration and therefor a differently structured x axis. My simple goal is just to have the graph display dose over time in a normal looking manner when you change from subject to subject.

let me know if anyone can help with this!