rota for reception cover

I need to devise an on-going 'cover' rota for 1 hour each day, split into 2
half hours, covering weekdays only, with 4 people performing the 'cover' - 2
people = 2x ½ hour per day.

I have dates down the vertical axis and names along the horizontal axis. I
need to show the number of 'covers' per person per week and a running total
of the number of covers. Any one of the 4 people may decide to take a
holiday at any time so the chart needs to show where some have done less and
some have done more.

Has anybody any ideas?