I've got a client that I've developed flash and html banner ads for in the past and now they're wondering if I can create a banner ad for them with dynamic text in it. For example, within the graphics of the ad, there would be a place that would say something like "Over XX,XXX copies sold" and that number would auto increment (every few seconds). The tricky part is that they want the number to increment based on a variable number that will be generated on their website, but the banners will be posted to various advertising websites around the web.

So, having never done this before, I'm thinking it will be some combination of php/javascript on their site to create the auto-incrementing variable and, within the html code of the banner, there would be some sort of javascript (with some Ajax perhaps for the continuous updating) to grab that number from their site and display it.

Anyone ever done/seen anything like this?? Anyone have any tips/advice? I'm sure it's doable, just a matter of figuring out the easiest/best/most reliable way to do it without spending way more time building it than needed.