How to put arguments in a function at run time?

So I am using execlp in my c++ program. execlp is of the form " int execlp(const char *file, const char *arg0,...,const char *argn)" meaning that it can take arbitrary amount of arguments. I just want to know that is there a way I can put arguments inside this function at run time? Since the arguments are provided by the user, there is no way for me to know the exact number of arguments. Of course I can pick a ridiculously large number from the start but that won't be very efficient.I need a more efficient way that would allow me to put arguments at run time.