I have a web form with a date input (actually 3 inputs [dd] / [mm] / [yyyy] - though I'm happy to make it one input box).
The form is used to enter a roster. Rosters begin every wednesday and are a fortnight long.

So I'd like a button of some kind next to the input which says "next". So if the date 18/03/2009 (dd/mm/yyyy) is in the box, and the "next" button is pressed, the date changes to 25/03/2009.

In addition, when you first open the page, the date box is blank, so I'd like to automatically populate that field with the next wednesday which falls into the fortnightly cycle.

I'm thinking something along the lines of: give the JS a start date, then it just counts up in fornightly increments until it gets PAST the current date - then populate the field with that date - then the "next" button would just add 2 weeks to the date already in the input field.

(In there somewhere id also like some validation in case the user enters their own random date)

Unfortunately, my programming is usually in php, and so im a TOTAL noob when it comes to javascript... any help would be great!

**Just so you know, im posting this form to google calendar which automatically syncs with my iphone!! L33t!! Haha...

Thanks in advance!