Can't you just use an array within a type?
Actually no, I can't do that.
Each index of the array represents a sector (solar system) within my game, and I use the types in those arrays to hold all data about a sector.
Doing the reverse is even more complex (for my game anyways).
Besides, when I'm reading station- and planet-data, I'm using 2-D arrays (and for commodities being sold there even 3-D arrays), so that's not an option.
@ TomToad: Thanks for clearing that up.
Now I see why it cannot be done (in Blitz anyway).