This sounds a bit silly bit after having searched for 3 hours I have given up!
I want random numbers in my patch, so I used random. But I don't want the same number twice. I want the number to be a different number than the random number generator has already given. (I can't use the "urn" function here because for instance if it has given number 1 it must give 2 or 3,4,5 etc. and if it has given 5 it must be able to give 1 again as a possible output (but not 5!))
Hope I was clear!