Sorry, I’ve never done this specifically with EAs. So I can’t provide any specific examples. You might be able to slide it in via the MP code, but I don’t know this for certain and probably isn’t supported.
For writing your own monitor, there is an open source community Citrix Management pack that can probably offer inspiration. This essentially drives Internet Explorer via COM objects to login to a webpage (Though I’d look at Selenium instead of IE).
Before heading down that route I’d have a chat with support. They might have a way of doing this in EAs or failing that have other ideas or raise a feature request for you.
Sorry I can’t offer you any specifics, maybe others have some experience with this sort of thing directly. Best of luck.