Random Selects Into Multiple Boxes?

I have a script which allows me to select random users from one select field to another and works like a charm, but...I want to be able to get random users from one select field to multiple (lets say 2) other select fields...So lets say that I have 5 users in the first field (select1):

James
Bill
Jennifer
Bob
Karen

Now when I press a button: <input value="" type="button" onClick="randomusers();" />

2 users should be moved to select2 and other 2 users moved to select3.My current script is as follows:

function randomusers(){
var given = 2, used = {}, randnum, opts = $('#select1 option'), olen = opts.length, hiddiv = $('#hiddendiv');
function ran() { // generate a unique random number[code].....