I am trying to create an average line across a current line graph. I would
like it to be based only one cell so that i dont have to update the x axis
every time more information is input into the spreadsheet.

Is there a way to just have a line that only has the Y axis change based on
one cell, and the X axis is not defined? I would like to have the line
extend to the end of the chart no matter what the x axis looks like.

right now i am usuing =SERIES("Average",,DATA!$M$4:$M$2401,2)
-i have to increase the 2401 number every time more data is added even
though the average is calculated in column M and just repeated over and over.
i have found if i dont increase that number the line stops too short on my
graph and is shorter than the line graph i am trying to compare it with.

Thank you!