Please replace the ??? with your data!
Hallo,
it's not a usual trouble with the form what's my problem, but a question of special use.
Is it possible to let the form receive a value via GET? To show what I want you can look at http://www.hl-ruegen.de, select "Ferienwohnung" in the navigation and click at "Zur Buchungsanfrage". Depending on which "Zur Buchungsanfrage"-link you use to get to the form, one of the checkboxes of the form is pre-selected.
I try to get the same, but don't know how to deliver the form data.