How to oblige Skype to use a proxy

Hello,

can someone tell me how to oblige skype to use a proxy. i have fill an ip adress of the proxy in menu options/connexion.
the problem that even if the proxy is down skype continue to be connected.

i want to oblige skype to use a proxy because i want to use a dedicated line for traffic skype.

There is another very easy test. il you fill any ip adress in options/connexion/socks5 and you stop and run skype it will be connected again
Some ideas