I need to make a report that counts how many calls were active at each second in time so that I can see the largest amount of calls we had going at any one point in time. All other details are really of little concern, all I need to determine is the highest amount of lines used and then I will adapt in things like how often etc at a later time.

To achieve this I have envisioned a report that groups by every second for say the last month but I have no idea how to do this. I cannot use one of the time fields, such as call start time because then I need to have a count formula tell me how many calls started before this time and subtract the calls that ended before this time.

I have a date and time field for both call start and call end.