You're going to be waiting a while on that one. SSViewer doesn't accept dynamic values for arguments in functions.

What I would do is just augment a static class variable every time the function runs

so..

static $form_count = 0;
function CalendarForm()
{
self::$form_count++;
// do stuff
return a form with id="some_form_".self::$form_count
}

Hey UncleCheese,
Just an update as to the SSViewer. Earlier today I managed to write the code for SSViewer to access dynamic values. I managed to get it to accept one value and then managed to fix it to allow for unlimited parameters to be passed. So, now it will work perfectly with dynamic values with/without control loops.

You can view my submission at: http://open.silverstripe.com/ticket/3633

Nice work. I would love to see this functionality integrated into Silverstripe. Anxious to hear what comes of it.