Display the break-even area on an excel chart

Hi Experts

I am constructing a break-even chart, based on the following data:

Output      Indirect Costs      Total Cost      Revenue
0              £40,000                      £40,000              £0
100              £40,000                      £52,000              £20,000
200              £40,000                      £64,000              £40,000
300              £40,000                      £76,000              £60,000
400              £40,000                      £88,000              £80,000
500              £40,000                      £100,000      £100,000
600              £40,000                      £112,000      £120,000
700              £40,000                      £124,000      £140,000
800              £40,000                      £136,000      £160,000
900              £40,000                      £148,000      £180,000
1000      £40,000                      £160,000      £200,000

The basic chart displays fine. However, I would like to include a box, that clearly shows the break-even point, as in the example below.


I would like this box to be part of the chart, so that it changes dynamically when you change the figures, i.e. in the above table, the break-even point is 500 units, but if I changed the revenue or costs, the break-even point would be higher or lower - I'd like the box to change accordingly.

Any assistance would be greatly appreciated.