script, random choice, n1=-1, n2=-1, n3=-1, n4=-1, n5=-1, n6=-1, n7=-1, n8=-1, n9=-1, begin
  variable(last)
  if(n1 > -1) then(last:=1)
  if(n2 > -1) then(last:=2)
  if(n3 > -1) then(last:=3)
  if(n4 > -1) then(last:=4)
  if(n5 > -1) then(last:=5)
  if(n6 > -1) then(last:=6)
  if(n7 > -1) then(last:=7)
  if(n8 > -1) then(last:=8)
  if(n9 > -1) then(last:=9)
  if(n10 > -1) then(last:=10)
  variable(r)
  r := random(1, last)
  switch(r) do(
    case(1) do(exit returning(n1))
    case(2) do(exit returning(n2))
    case(3) do(exit returning(n3))
    case(4) do(exit returning(n4))
    case(5) do(exit returning(n5))
    case(6) do(exit returning(n6))
    case(7) do(exit returning(n7))
    case(8) do(exit returning(n8))
    case(9) do(exit returning(n9))
    case(10) do(exit returning(n10))
  )
end

plotscript, example, begin
  show text box(random choice(15, 27, 4, 250, 252))
  wait for text box
end