I need help calculating the "occupancy rate" of a lodge.

Hello there. I have a spreadsheet that shows check in, check out times for guests in 5 units: unit 1, 2, 3, 4, & 7 (5 and 6 aren't being rented).

I would like to have a chart that automatically displays the occupancy rate for each room as a guest is entered into the table. I'm not great at all with charts in numbers and another difficult part is creating formulars that detects the changes of a new month. So I've drawn a rough draft of what I'd like the chart to look like. Can anyone help me come up with a formula to make the chart display this?