Gap to Target Column

I want to create a chart that shows "Gap to Target. Please see attached Sample spreadsheet for more info.

Note how the yellow part of the chart is formulaic...is actually the chart...and the green bar over it is manually pasted. That green bar is supposed to be "result" and that yellow gap is supposed to represent the difference between Targeted sales and the actual Result.

Any guidance on how to actually build the green part into the chart? Every time I try, it just adds them together and doesnt show the gap. Any thoughts appreciated.

Thanks,
Dom