The command 'rand' generates a random number from 0 to 65535.  To restrict that range to a smaller range, you can use the modular arithmetic operator ^ like so: rand^37.  This divides the random number by 37 and returns the remainder.  By the nature of the remainder, its range is from 0 to N-1 when you divide by N, so this function returns your desired number from 0 to 36.