Millisecond Forums

Hello --

I am using the standard randomized Subject ID script to assign subject numbers for a Web experiment, which is the following:

function GetSubjectNumber()
{
    var snum = Math.floor(Math.random() * 1000000000);
   return snum.toString();
}

But for some reason several subjects (about 10) were given the same subject number when taking the survey. I know this isn't supposed to happen when it's randomly assigning numbers between 1 and 1000000000, but it is. Has anyone had this bug, and how might I correct it?
I need to have an even number of evenly-numbered and odd-numbered subject IDs.

Thanks,
Josh