Self-updating place or event markers in Google Maps: possible?

Shortened link for this post is http://is.gd/oGokQH

Usually when I think of something I would like to do on the internet I find that someone's already come up with a neat solution, or knows how to. I'd be surprised if I'm the only person to have thought of this 'gap' in the market but a quick Google search for 'google maps markers update' brought me to pages of stuff I really didn't understand, for example...

http://groups.google.com/group/Google-Maps-API/browse_thread/thread/3543780d6a588432?pli=1

Imagine I create a map of locations in London which are showing open air film screenings. There might be one in Wandsworth on 20 July 2011 and one in Clapham on 14 September 2011. When I added both of these screenings, say on 8 July 2011, they were green as in 'yet to happen', but now, on 13 August 2011 the Wandsworth one is finished but the Clapham one's in a couple of weeks.

Is it possible for the place/event marker to automatically change its colour once the date has passed? How do I get in touch with Google people to ask them? Is this a task for Google+?

I don't want to delete it because that stops conveying any information (and the information is "Wandsworth showed a film in 2011 perhaps it might in 2012, might be worth making a note of the website to which this marker points").

While creating the Open Air Cinema Screens post I made very good use of out-of-date information to help me find newer information. No good at all if stuff disappears.

Those 'concertina' things on web pages

While I've got your attention I'm also interested in what I think are called concertinas. These are collapsible bullet-point type lists which can be expanded / contracted depending on which bit you want to look at. Ideal for cinema listings but alas I don't know how to make them happen in Blogger. Or WordPress or any other blog platform. Do I have to get my own website to make that work?

I've tried pinching the code and using the 'edit html' button when editing a blog post here but didn't work.