Proxy custom test - how to setup?

Hi,

I m searching for how to setup a custom test rule for proxy manager but find nothing.

I realise that proxy manager cant detect speed of all proxys during test proxy function.
It causes fault filter results when I use automator to delete slow proxies, because proxy with no speed detected remains in list.

Is the proxy custom test a workaround for this need?
Even if not so, I would to know how to setup a custom test rule.

Thanks in advance guys!
This forum is getting even better every time.

Marcelo