Hi Heather,
Take a look at this blog post:
http://frameautomation.com/run-a-script-in-response-to-a-command/
Basically, you have to figure out if there is a unique function code for deleting a marker. I would guess that there isn't, but it is worth a try. Otherwise, there may be a workaround. Let me think about it. In the meantime, I would follow the steps in the blog post and see how far you get. Note that this works with FrameMaker 11, but it may not work with 10.
Rick