4 digit random number

Hi guys,

i would like to have a text layer that changes it´s 4-digit number everytime it´s duplicated.

I found an expression that basically does that, but it also includes other values like "@" and "%".

s = "0" + Math.floor(random(10000));

while (s.length < 4) s = "0" + s;

The solution must be simple, I just really suck at expressions

Thanks for the help.

Cheers,

Björn