Create a variable called "counter". Than use "is element exist" to check if element exist and update "counter" variable whenever element is missing. Check counter variable in the loop, and fail thread if "counter" hit 3
As already stated, 2000 http client threads. 2000 browser threads would be quite an intensive operation to say the least... You would need a very powerful vps with lots of RAM, but even then I'm not sure BAS would handle it without crashing.