linking a page to the appointment

On a real estate site I would like to offer a "schedule a showing" link on property pages. I would like that to link to the /make-an-appointment page and somehow pass through a value to the appointment ... even if I could simply dump the URL into the appointment form in a hidden field it would work to know which property they wanted to see.

I'm sure others have had situations where it is not feasible to maintain an inventory of "products" (houses for sale) and wanted to do something like this? Thanks!