Have a look at this product. I recommended it to one of my clients (in place of paying me to develop a similar system from scratch), and they are very pleased.
Might be much cheaper than your time to try and develop something with this much power …
Peace, love & brown rice,
FileMaker + Web: Design, Develop & Deploy
Certifications: FileMaker 9, 10 & 11
<http://www.onepartharmony.com/> One Part Harmony
Austin, Texas • USA
Hundreds of them here: http://developer.filemaker.com/search/
Likely even a few in your area.
But as Morgan says, it'll be much less expensive to buy something off-the-shelf and then customize it then would be developing something custom from scratch.
Unlike many of the FileMaker consultants in the marketplace, we typically 'support' developers as opposed to building a solution from end to end. If you built something yourself, or found a template which you need additional functionality beyond your abilities; we do a lot of modications and 'fix-it' work.
If you are looking for a consultant to take the project from 'end to end', we work with dozens of full-time developers and we can give you some advisce on who we think may be a good fit for you. We do not get paid for these referrals, and our advise is not baised beyond the obvious, but we are in a unique position to see code from numerous vendors running on our servers and we get feedback from our common clients. We can give you more of an objective review since every developer will 'claim' to be wonderful on the job boards.
If we help you find a quality, affordable developer which matches your requirements, then you are more likely to utilize our hosting services when they get the job completed. If we recommend a 'hack', then they are less likely to finish and we are less likely to see you as a client.