WP Booking Calendar plugin: we need an expert on it

Hello, we are working with an old version of the WordPress Booking Calendar plugin ([login to view URL]). We don't want to upgrade the plugin because we have modified it, and we prefer to stick to it. We use it so people can book vacation rentals (houses). What we need: ----------------------- Usually the plugin can search by "check in / check out" dates, so free houses come up. We want to add a "duration" dropdown (7-9 days, 10-13 days, 14 days, 15-19 days, 21+ days), that would show houses that are free for that X number of days in a *given period of time*, specified by the check in / out date picker. So: - if you use check in / out dates only, the search is normal, and we show available houses in that exact, fixed period. - if we use check in / out AND Duration, we take that period of time, and we show available houses that are free for those selected X days *inside the period* (flexible dates). I guess this would be possible using jQuery on the search form itself, but I'm not sure. Maybe PHP is needed. Here's an example of what we want: - [login to view URL] Where it says "Wann" is the check-in / out. Where it says "Dauer" is the Duration (X days). We need someone experienced in Booking plugins, and familiarized with the WP Booking Calendar plugin in particular. I will provide access to a test environment, and when all works as needed on the live site, the payment will be released. We will be available all the time and we prefer a fluid, constant communication with you. Thanks,