Booking with flexible dates

Hi

I am interested in new feature for rooms

There are no flexibility of dates .

I would need in the form an input select with "+ or -" nights

Here is an example of what the customer would like

http://thelisresa.webcamp.fr/?camping=amandiers&lang=en&PHPSESSID=uf0nb4...

I think it could be a module add on to rooms (room flexibility ?)