Help with creating a function file

How do you write a function with the name ”min_ode” and call it by ”[t,U]=min ode(f,I,ua,h)”. This should solve initial value problems. f is the function, I is the interval [a b], ua is a given number such as u(a)=ua and h is the length of steps.It should return t and U that is two vectors. Ex:

[t,U]=min ode(@fun,[1 4],2,1e-3)