How Does one go about setting which column to select from for a relate field?

What we want is that on two custom modules, when one clicks on a Reference number it shows the full details of the other module, and vice versa.

The reason is that we have a module which contains the names, address and contact of those currently leasing blocks and another module which contains the management company and charges for those blocks as well as the address of the block.

We want rather than having one giant module with all those details, to have two smaller modules that you can click through to each other quickly.