Folks
I need to schedule 1500 ish engineers to bring the mobile phones in to have a manual update applied to them. stop laughing.

It simply need to
ideally pick up their details from AD
let them select from a drop down of locations to visit
let them select from a list of dates when we will have an engineer at that location to do the update
Let them select a time that isn't already booked
make the booking.

Dead simple, so does anybody know of a web app, or ideally sharepoint plug in / web part to do this? Trying to get something written will take for ever.