Can one module save a record with a foreign key to a record in another module's table?

For example, I have an Events module on a page and I have saved a bunch of races on the calendar.

I'd like to write a module that allows the logged in user to select one of the events entered on the calendar and record a result for that event, then show a list of all their entered results.

I understand that modules are meant to be modular and perhaps this goes against the design philosophy of DNN, but it seems like I should be able to do this (it works for user data, right?), I'm just not sure where I would start.

Can anyone suggest a way to make this work, or perhaps a different way to go about it?

sure you can create a custom module with any data reference, even to existing modules, however, this is NOT recommended, due to upgrade issues, if the base module changes its data structure and the FK reference interferes with the upgrade. you should rely on the business layer of the other module and your module should clear references in business layer - this would work even with both modules using different data stores.

However, be aware, that modules, other than the DNN framework itself, do not necessarily provide version backwards compatibility, because this is a quite rare use case. I.e. you should test your module with any new version explicitely