Move it out of the cache block, this kind of functionality is not currently possible I'm afraid.
It is possible in the template component, and ez publish 4.0.
You can read more on it here: http://ez.no/doc/components/view/trunk/(file)/introduction_Template.html#caching
ps:
{set-block scope=root variable=cache_ttl}0{/set-block} is for view-cache, not cache block
