Right, I've integrated the popup calendar from DHTML goodies. This basically means that an extra stylesheet link needed to be added to the new_topic_form.asp page. If you don't add that stylesheet link, it looks an absolute mess !!! The below screenshot shows what it looks like with the stylesheet, nicely formatted (but so far all this is untested in FF)
Once you have posted this new topic, here's how it looks on the calendar.asp page

You can now see the multiple entries for this calendar, for 2 events. There doesn't seem to be any issues with the overlap or anything like that. The weekly calendar page still needs modifying to include multiple day event support. I will also go in and add some js validation so that when the event start date is changed, the event end date is automatically the same. Whoever takes this MOD on, I'd add some server side validation to do a check to make sure the start date is less or equal to the end date.
Just to add to your point on the last post, AJAX wasn't really developed for the "old" ASP language anyway, it's more of a .net thing from what I can see. For me though remote scripting is the best way forward. Maybe I'll get round to learning .net one of these days, or maybe I'll wait a good 10 years until they phase ASP out. Seems to me that whatever ASP.net can do ASP can do just as well, ASP just isn't as simplistic and straightforward.