I assume you are getting an error with this calc? You can try (untested):
IF sum([Commission amount]) > (sum([Median])*1.20) THEN 1 END
If this doesn't help, can you post a packaged workbook that demonstrates the problem and let us know what error you are receiving?
I realized i never got back on you regarding my question so apologies for that. Appreciate your time to review and propose way of resolving it. The formula that you proposed did not work, but in the meantime i was asked to display average and stdev. I added a trend line on the graph and added the standard deviation of -1;1 based on the average. That solved the issue for this piece of work.
No problem; please mark your question answered (you don't have to mark my reply as the correct answer, you can mark it as "assumed answered") so other helpers know this issue is resolved. Cheers!