on mouseUp
  ask "Number1:"
  put it into num1
  ask "Number2:"
  put it into num2
  put "gcd(" & num1 & ", " & num2 & ") = " & gcd(num1 &","& num2)
end mouseUp

function gcd params
  put item 1 of params into num1
  put item 2 of params into num2
  if (num1 > num2) then
    put num1 into temp
    put num2 into num1
    put temp into num1
  end if
  repeat forever
    put num2 - num1 * trunc(num2/num1) into num2
    if (num2 is 0) then
      put num1 into gcd
      return gcd
    end if
    put num1 - num2 * trunc(num1/num2) into num1
    if (num1 is 0) then
      put num2 into gcd
      return gcd
    end if
  end repeat
end gcd