Help with transitions for randomly loading external swf as backgrounds

Hi there,
I hope someone out there can help me. I am using flash 8 and am fairly new to actionscript. I have successfully coded my backgrounds to randomly change every minute. The problem is trying to code it so they fade in and fade out. I have searched and posted on various forums, and there are lots of posts on fade transitions with buttons, but that is not what I am looking for. I will post my code and if anyone could help me with integrating a fade in and fade out I would greatly appreciate it. I should not that my external files are a few lines of code, that generate a gradient to fill the stage, the site will be a full browser flash site.

//have a random number between 1 and 10
var randomNumber:Number;
// set interval… for x minutes
var id:Number = setInterval(this,“loadfunction”, 60000);
// make a function with a switch that takes a random number
// and loads a movie

function loadfunction(){
randomNumber = int(Math.random()*10);

switch(randomNumber){

case 1:
loadMovie(“bg1.swf”, 1);
break;

case 2:
loadMovie(“bg2.swf”, 1);
break;

case 3:
loadMovie(“bg3.swf”, 1);
break;

case 4:
loadMovie(“bg4.swf”, 1);
break;

case 5:
loadMovie(“bg5.swf”, 1);
break;

case 6:
loadMovie(“bg6.swf”, 1);
break;

case 7:
loadMovie(“bg7.swf”, 1);
break;

case 8:
loadMovie(“bg8.swf”, 1);
break;

case 9:
loadMovie(“bg9.swf”, 1);
break;

case 10:
loadMovie(“bg10.swf”, 1);
break;

}
}
loadfunction();
Again I would greatly appreciate any help, as I am pretty confused.
Cheers