When has a cuePoint in Video Loaded?

I’ve been working through a tutorial on the Adobe Macromedia site which has an Flv video (Progressively Downloading), and buttons at the side which jump to certain Cue Points within the video.
http://www.adobe.com/devnet/flash/articles/vidtemplate_mediapreso.html

What I want to do is to only enable the buttons when the video has loaded in enough to reach that particular Cue Point.

If for instance you view the video, and immediately try to hit the last button (which jumps to the last Cue Point) then there is a massive delay while you wait for the video to load in before it eventually goes to that Cue Point.

Can anyone help?