This is exactly what i'm trying to figure out.
How we did the same thing here:
1. Employee fills out a FormsCentral web-based form for the vacation request.
2. E-mail response goes to employee, with directions in the e-mail to forward to her/his supervisor. This step is necessary as a way to ensure who is actually requesting the form. If the form bypassed this step, anyone could submit a vacation request for anyone else, and you wouldn't know for sure if it was a legitimate request.
3. Employee forwards to supervisor.
4. Supervisor replies back with approval or denial and cc's person who tracks vacation requests. This creates a "paper" trail via e-mail, in case there are ever any concerns.
I hope that helps,
This sounds like a good plan.