I have been asked to plot a chart to show time taken vs a service level agreement. Both are provided in date format (No time) in a master data sheet. Basically the task in question has a 48 hour SLA. I don't really want to edit the master data sheet by adding any helper columns.

I have 2 questions regarding the above:

1. Can anyone suggest which chart would be best for this?
2. Is there any way of doing this without helper columns.