How to generate 16 digit unique random alpha numeric numbers?

Hi
Try this formula:

=RANDBETWEEN(100,999)&CHAR(RANDBETWEEN(65,90))&RANDBETWEEN(1000,9999)&CHAR(RANDBETWEEN(65,90))&RANDBETWEEN(10000,99999)&CHAR(RANDBETWEEN(65,90))&CHAR(RANDBETWEEN(65,90))

Good luck.
Tony