ASP 产生不重复的随机数

没什么说的，就是生成随机数而已！！
程序代码
<%
Function gen_key(digits)
dim char_array(50)
char_array(0) = "0"
char_array(1) = "1"
char_array(2) = "2"
char_array(3) = "3"
char_array(4) = "4"
char_array(5) = "5"
char_array(6) = "6"
char_array(7) = "7"
char_array(8) = "8"
char_array(9) = "9"
char_array(10) = "a"
char_array(11) = "b"
char_array(12) = "c"
char_array(13) = "d"
char_array(14) = "e"
char_array(15) = "f"
char_array(16) = "g"
char_array(17) = "h"
char_array(18) = "i"
char_array(19) = "j"
char_array(20) = "k"
char_array(21) = "l"
char_array(22) = "m"
char_array(23) = "n"
char_array(24) = "o"
char_array(25) = "p"
char_array(26) = "q"
char_array(27) = "r"
char_array(28) = "s"
char_array(29) = "t"
char_array(30) = "u"
char_array(31) = "v"
char_array(32) = "w"
char_array(33) = "x"
char_array(34) = "y"
char_array(35) = "z"
randomize
do while len(output) < digits
num = char_array(Int((35 - 0 + 1) * Rnd + 0))
output = output + num
loop
gen_key = output & year(now) & month(now) & day(now) & hour(now) & minute(now) & second(now)
End Function
strrad=gen_key(5)
response.Write(strrad)
%>