Help with casio fx-9860G

Question

I need help writing custom functions for my casio fx-9860g

I have done this before in my Texas Calc but Im not sure there is a way to it with casio calculators... say, for instance, I want to write a simple function like so:

public int triple(int x)
{
return 3x;
}

I understand this is quite a simple function but I want a way to store some formulas so I can quickly calculate stuff without having to rewrite the formulas all over again.. thanks in advance.