how to end or exit the running script

[bighalo]

I wrote a vbs:

sub main()
...

do
  nIndex = objTab.Screen.WaitForStrings(g_vWaitFors)
  if nIndex = 1 then
    ...
    <do something>
    exit sub
  end if
loop

end sub

I waitforString and do something only once.
I use "exit sub". But the script still running in loop.
How to end or stop the running script?
Is there any code available? Not Script/Cancel menu.