Something like:
Code:
on *:START: sockopen VersionCheck.YourScriptName www.mysite.com 80
on *:SOCKOPEN:VersionCheck.YourScriptName: sockwrite -n $sockname GET /path/to/MyVersion.txt
on *:SOCKREAD:VersionCheck.YourScriptName:{
  var %version  
  sockread %version  
  tokenize 32 %version  
  sockclose $sockname
  if ($1 > %Version.MyScript) {
    if ( $input(YourScriptName has been updated $+ $chr(44) goto the website?,y,Update available) == $true ) {
      run http://website.com/download.html
    }
  }
}