Simple Mitigation method to prevent exploit using function pointer overwriting( for sale )

Some heap overflow exploit overwrite function pointer ( including C++ vptr ) .
Function pointer itself can not be protected effectively.
But exploit using function pointer overwriting can be mitigated effectively under DEP.
if extra 2 or 3 instructions can be  executed at each function pointer call  ,
it is very hard to exploit successfully.

If you are interested in my idea , send mail to ohojang@gmail.com