Nearest neighbors for TSP

Hi there,

I am trying to implement some form of heuristic for the TSP where I'm decreasing the size of the model by restricting the declaration of variables X(i,j) to those combination (i,j) for which j belong to the, say, 10 cities nearest to i. Here X(i,j) is an binary variable indicating whether or not edge (i,j) is in the tour.

I created a subset of the cities to find the nearest neighbors of city i, but how can I implement it in the model? Do I need to add an extra constraint or?

Added you'll find the code of my AIMMS project.
Thanks in advance!