Chart Axis Scale Editing - Positive and Negative Independantly

Hello Excel Geniuses.

I have an issue with charting, I've looked on google all over and havent been able to find a solution. Basically I want to be able to edit the vertical axis's of my chart independantly, aabove and below zero. Here is a photo of my plot as it stands now:

\1

As you can see, the range above 0 on the vertical axis for the blue line "horiz displacement" is well spread out, but the line contains little detail. Conversely for Series 2 (-ve y axis data, RED LINE) there is alot of detail, but since this ranges only between 30 units it is squashed and you cant see any detail.

I need to make it so that the unit ranges above 0 on y axis are (0-80) but only marked every 20 units and squash this top section of +ve y axis data to about a 1/4 of the whole chart. I also want to blow up the data below y axis zero, obviously with a different range than for the blue data, and have this displayed as the remaining 3/4's of the chart as this is the most detailed section.

Everything I read online to help only talks of editing the entire vertical axis steps, however I want to edit above and below 0 differently.

Hope you can help, I really would appreciate it!

Biggie9