Update Calendar on 3rd Party Site automatically w/ Macro?

Looking for a solution that would allow us to update reservation calendars on 3rd party sites ([login to view URL], [login to view URL]) when they are updated on our site. The 3rd party sites are used for marketing and accounts with them are password protected. Our site is Drupal based, using the Hotel Booking module calendar which in turn uses the Drupal Date API. Any sort of solution could be triggered every time an Ubercart order is completed, since this is when the calendar is updated. Really have no idea which sort of programming knowledge I should be looking for, and what sort of budget. Please bid with a simple outline of your approach, so that I know you read this project description.