A question about Memoize

I am running a simulation that in some places consists of functions, which in turn have functions. The end of one of these "branches" computes nchoosek matrixes, and the batch of nchoosek computations are the same throughout the simulation. Is it sufficient to set the Memoize function inside the computing function, or, should it be placed in the main code to ensure full use of Memoize is achieved. If so how?