SFML provides a delta time function.
sf::Time dt = deltaClock.Restart();
from : http://en.sfml-dev.org/forums/index.php?topic=7068.0
Basically what you could do is create a class that holds pointers to functions you want to call. And for each function you have a "clock" ( a simple float or int ) in a time table(Array/Vector) that is iterated over in combination with the delta time to see if x amount of seconds have passed. If so you do a callback on the associated function.
I'm not that much deep into C++ and there is probably a clever way to do it.
There is also this :
Which is build ontop of SFML but it requires C++11. It's an unofficial extension library that has some great event triggering functionality.
On the upside of C++11, it supports "function" objects. Which help ease out some function referencing.
Also google for events and C++ if you really want to dive deep into it.