How to prevent caching of result for a perticular call?

Let's say for example a result of  function X(a,b), set for caching using Admin
console.

In the function X(a,b) under certain conditions, I don't want to  cache the
result. I would like the next call to function X(a,b) with same parameters to be
excuting body of the function rather fetching the results from result cache.

Basically the question boils down to
1) In the function body, is there way to give a hint programatically, not to
cache the result.

2) similarly is there way for the calling function to force a read through?

I hope my questions make sense, otherwise I can describe function call sequence
to describe the issue.