HTML/PHP to auto-login and post from external webpage

[IdealExchange]

I am webmaster and vBulletin forum admin (3.6.8) for my World of Warcraft guild. I'd like to code a web form for guild applications such that pressing "Submit" will post the filled-out form to a specific thread in my guild forum. For example, the user would fill out the following HTML form:

Name: [NameField]
Age: [AgeField]
Question 1: [Answer1Field]

...and, on pressing "Submit", the page would log in to a special account on my forum, reply to the Applications thread, and post:

Originally Posted by GuildApp

Name: stuff from NameField
Age: stuff from AgeField
Question 1: stuff from Answer1Field

Is this possible to accomplish efficiently, and if so, how would I go about it? If it isn't, I can always just have it email the apps to me and post them manually, but I'd rather have it done automatically (and I like to expand my coding juju whenever possible).

Your help is appreciated!