Setting up reservation microflow to stop double booking given specific parameters

Hello, I am trying to set up a reservation system but am quite unfamiliar with mendix. I know my domain model is not as simple as it could be but it was required by my assignment that I have multiple objects. I just need to check the database for other reservations that have the same start time and stop time or anything in between given they also share the same room number. So if a Room has this time slot taken then delete reservation. Here is my domain model as is. 
1 answers

The school is using the same problem :). It has been answered before in the forum: