I very much doubt this is going to provide you what you want. When a machine connects to the network it requests an IP address, and you may through a lookup or another system be able to identify exactly who that machine belongs to. However, very few machines will release an IP address ‘cleanly’, most just go out of range and the lease on the server eventually expires, so you have no idea when a machine actually left.
If you want to go down an automated attendance path then you might be better off using a location based system, either using the Meraki location APIs to determine which machines are onsite, or using another application (e.g. who’s on location) that can interface with the GPS locator in a device.