firefox cookie add programatically

Hi,

I want to set a cookie for firefox from my c/c++ program on windows for a
specific website.

I am able to do the same in cookies.txt file but It works only if Firefox is
closed before updating this file and Started firefox after updating the
cookies.txt.

but not if any instance is running. please let me know if there is any way
of doing it.

thanks in advance
kapil