Reporting on Completion of Recurring Tasks

I have a series of tasks that I try to complete every day (exercises to keep my back healthy). I would love to be able to create a report which shows what % of days I’m actually accomplishing this goal.

I was thinking that I would need to write an applescript that would monitor Omnifocus and when my “Daily Back Exercises” project is completed it would then log that into a spreadsheet somewhere.

It seems that Omnifocus only supports AppleScript connected to a button though. Am I misunderstanding? How might you go about accomplishing creation of such a report?