All it does is accept an input time and calculate when the initial and subsequent doses should be taken?
(I had a colonoscopy once, and, boy, were those, er, "doses" fun!!!)
Any particular choice of development platform as long as it's Web-based? Not much really required here other than, say a Java applet. I like to stick to the traditional approaches that are no fuss, no mess, rather than jump on every bandwagon where we can't type the letter 'A' without ActiveX objects and QuickTime movies.
You could even create and auto-populate an on-the-fly Excel worksheet and post it to the client for fingertip download.
Yes, quite obviously.
Actually, it seems rather odd that you are out here trying to procure professional services without an idea of what the task actually requires. That's a good way to be burned by whoever happens along and glad-hands you and sports a flashy necktie.