How to reload monthly calendar passing service as parameter

I would like to let the user select the service not using the [app_services] drop down, but clicking on a button near the description of the service he wants to book.
Please see http://staging1.adventurerooms.it/en/booking/
You need username/pw to access:
Username: adventurerooms
PW: adventurerooms2014
Here I'm creating a general description of the service and some variations. Each variation has a different price. For each variation I included a button to book it.
When the user clicks on the button I would like to show the calendar ([app_monthly_schedule]) where he can select the date/time and finalize the booking. So, from the button I should call a different [app_monthly_schedule service = "selected service by button"] for each button.
How can I accomplish this ?
I could create different pages with a different monthly calendar in each, but I would better like to place the calendar in the same page where the user select the service.
Thanks for your advice
Kind regards
Antonio