I wonder if anyone has done this and could give me some pointers on how to proceed.

Let's say I have two Custom User Attributes;

- Fav Fillings (Fish, Ham, Salad)
- Fav Bread (Sandwich, Roll, Baguette)

Then, I want to have Fav Combos;

- Fav Combos (Fish+Roll, Salad+Baguette, Ham+Baguette)

..where the Fav Combos attribute takes a FavFillings.ID and FavBread.ID to give me a join on the two.

I guess I need some pointers on how to approach this, and I also need to know if (over thousands of users) would I be able to efficiently search users by FavCombos?

Thanks