asp 随机生成字符

<%
function rndNumLetters(num)
randomize
dim num0,num1,num2,num3,pass
if num = "" or not isnumeric(num) or num < 1 then
num0 = 6
else
num0 = num
end if
do while len(pass)<num0 '随机密码位数
num1=cstr(chr((57-48)*rnd+48))
num2=cstr(chr((90-65)*rnd+65))
num3=cstr(chr((122-97)*rnd+97))
pass=pass&num1&num2&num3
loop
rndNumLetters = pass
end Function

response.write(rndNumLetters(7))
%>