Loading Movie using URL in param variable

programming flash
1

I’ve made an FLV player and it works like a charm when the location of the FLV is hardcoded into the actionscript inside the player, but i’m having trouble making it load a video dynamically depending on variables passed to the flash within the param tag, can someone please tell me where i’m going wrong?

first frame actions:

loadvid = new LoadVars();
loadvid.load($video);

MovieClip Actions:

onClipEvent (construct)
{
     contentPath = $video;
}

When i publish this movie the output debugger says:
Error opening URL “file:///C|/Documents%20and…/Desktop/undefined” obviously because i haven’t defined $video for the movie, but when i define it in the html it doesn’t work.

When i have the following setting hard coded in the movieclip, it works:

onClipEvent (construct)
{
     contentPath = "http://www.domain.com/video.flv";
}

any help would be greatly appreciated,
if you would like to look at more of the source, gimme a shout.
Thanks.