I assume you want to disable cache by looking at an info on html or url. I suggest you to place this info in HTML between unique tags. You could parse it using string operations after.
If you are using url you should use something like query string.
Finally disabling cache is done by
[[NSURLCache sharedURLCache] removeAllCachedResponses];
[[NSURLCache sharedURLCache] setDiskCapacity:0];
[[NSURLCache sharedURLCache] setMemoryCapacity:0];
However this code disables cache for good. If you want to enable it again you should set disk capacity and memory capacity to a higher value.