You can make the function it’s own method and just call the method whenever you want to do the calculation.
private void yourmethodhere(some parameters if you want)
{
do stuff here
}
Then whenever you want to call it, just use
yourmethodhere();
If you look at this old thread about writing CSV’s you can see the method addDataToCSV that is called from other places in the code. Then you can use it whenever you want, but only have to maintain it in one place.