Possible to Create a Custom Serial Number?

I have a software package that I wrote that is downloadable from a website.
I was using a VirtueMart hack to create an md5 Hash that was turned into a Serial # which could then be entered into the program to licence it.

The output looks something like this:
Joe Smith
4E01-D731-2A87-FA89-FA12-D188-0429-B890-00
I have attached a screenshot of the licensing screen that is in the software package so you get the idea.

$secret = "supersecretvalue";

	$demo = "00";
	$demo = strtoupper($demo);				// make $demo UPPERCASE
  	$h = md5( $this->orderdetails['details']['BT']->cust_name . $secret );  	// generate hash

	$h = strtoupper($h);				// make hash UPPERCASE
	$h = chunk_split($h,4,"-");			// add hyphens after every 4th character

	$h = $h . $demo;			// add demo to end of the license