Different timeouts per HTTP check

Hi,

I'm using a few HTTP checks to see how fast (and if) a website responds. However, some are known to be slower than others and I want therefor some sites not to trigger an alert or at least not if it doesn't respond in 10 seconds, but for instance 20 seconds. How can I achieve this for 1 check, not globally for all HTTP checks?

Best regards,

Wouter