Creating contact grid file for 2 independent grids.

[MIDHILAVARNAV]

I have 2 grids which are running independently one of a larger region with coarse resolution and other within the larger region and smaller in domain and of higher resolution. The grids are needed to be nested, to create contact point file I used contact.m but error of non existence of contact point pops out. Please help to resolve this issue. But if I create using coarse2fine.m for the creation of the smaller grid it creates contact file. I have read in papers people nesting two different independently created grids but don't know how they do it.