Hi Teetach Koomkaimu
Step1: In the calender widget set the event entity as the entity which you created and title attribute as the Room.
step2: Set start and end attributed as the time long
the Customer booked the room for.
step3:In events call a microflow to show a page and create a microflow to give data source for that data view in page.
step4: In data source microflow retrive the details and in the page place a dropdown. Now you can see the room occupied by the Customer in the calender.
I hope it will be useful..