Mine

on *:JOIN:#: {
  ;read the first wb for the user
  %wb = $readini($mircdirWBs.ini,$address,1)
  if (%wb) {
    var %i = 1
    ;calculate how many WBs the user has
    while (%wb) {
      inc %i
      %wb = $readini($mircdirWBs.ini,$address,%i)
    }
    %i = %i - 1
    %x = $rand(1,%i)
    %wb = $readini($mircdirWBs.ini,$address,%x)
    /msg $chan -WB $nick - %wb
  }
}