Conditional Formatting / Line chart help needed

Hello all! I want to introduce myself for a minute before I jump into my issue, as this is my first post.
I'm new to the forums and also pretty novice to Excel. Due to my job, my boss has put the tasks of Excel workbooks on my shoulders for creating and maintaining. My skill level is above normal, but no where near where I should be. I'm 26, decent with computers, and a gamer.

I use Excel 2013, but I need to keep it 2007 compatible for work as that is what they run.

Now to my problem...

I am creating a workbook with a master list of the next 7 years (2020) for Audits being performed. The data in the charts is individual, but I made a spot to the side of it for cumulative numbers for each row. He wants these linked to a line graph displaying the cumulative numbers. So each line is the year, the bottom shows the months. But using the cumulative numbers (the formula is =sum(d5:o5)), the line continues on the last number input. I need the lines to be dynamic with the information I put in but hide the repeats at the end until more is in. An example is (Jan - 5, Feb - 11, Mar - 16, Apr - 32, etc). If I don't add anything after april (until we have the numbers), it keeps repeating 32 at that point. Is there a way to hide that part of the line in the graph until information is plugged in?

Thank you all for reading and if you need more clarification please ask.

-Derek

I solved the issue!

Just to help anyone whom may have this issue, to do this you need to edit the cumulative values to be as a =if formula.

I.E. =IF(A1="","",sum(A1:A5))

That will add A1-A5 and if nothing is in A1 it will return blank. Thus clearing the line graph. I hope this helps someone down the road!

-Derek