Need help, Codes to block spiders except google.

<%
dim spider
spider=Request.ServerVariables("HTTP_USER_AGENT")
if instr(spider,"ALL Spider's characteristic STRING")>0 and not instr(spider,"googlebot")>0 then
response.Write("pass it.")
response.end
end if
%>

I want to block all the spiders except Googlebot, what's the characteristic string of all bot and spider?
Any guys can help me ?

 

I had use robots.txt,but it seam not work right?

User-agent: Googlebot
Disallow: /help/
User-agent: *
Disallow: /

 

I seem to recall reading that the Robots.txt was your best bet, but even that did not work 100% of the time.

I don't think it is possible without knowing either the IP address(es) of the bots or some kind of signature they each have.

 

I think it can also be done with .htaccess

 

oh it's easy
use this : " if instr(spider,"googlebot")<=0 then "
it means it will pass unless it's google

 

User-agent: Googlebot
Disallow: /help/
User-agent: *
Disallow: /