I don't kow your level in FileMaker.
If you feel you can do it on your own from scratch, just go.
I made one years ago, for an exibition center with 28 different 'rooms', with a control system for possible double booking.
I recently rebuilt it FM8, and it's much simpler now than 10 years back.
On the other hand, if you never did something like that, it could be easier to take the Seedcode example (or every other freeand open example) and modify it to your needs.
Once you have the grab of the concept, you can start building your own custom made application.