Use RewriteMap return value in another RewriteMap lookup inside a RewriteCond / RewriteRule

Currently I am working on ReWriting some URLs based on the
subdomain name provided (e.g. you type Restaurants.JCBauza.com and it takes you
to a page that is dedicated to restaurants.) Seeing that different content
lives on different directories, I wanted to facilitate the process of URL Rewriting
from the administrator's perspective. 

The issue: When rewriting an URL you have to map Restaurants to
/wikis/ListofRestaurants/ or something like that. Let’s pretend you have a
large list of restaurants (Restaurant A, B, C, and so forth) and they all live
on /Restaurants/NameofRestaurant.aspx. The issue here is that as the path of
the folder increases in length, having to write that down for every mapping
makes it really hard to read, and as you increase the offerings in your site
(e.g. Restaurants, Bars, Dealerships, Airports, Hotels, Books, etc) your URLS
are all different. In order to decrease the mess I created 3 files that hold
different kind of mappings. The first one named "Folders.txt" is a
list of the directories or FOLDERS were the pages leave and a key to find them
(let's call it TYPE). Example, TYPE "RESTAURANTREVIEW" is mapped to
"/wiki/Restaurants". File "Types.txt" holds all the
possible SUBDOMAINS and then a TYPE associated to them. So, SUBDOMAIN
RestaurantA is mapped to TYPE "RESTAURANTREVIEW". Then finally, file
"URLMap.txt" would hold the SUBDOMAIN and the PAGE you need to go to.
So SUBDOMAIN "RestaurantA" will go to page
"RestaurantA.aspx". Then the trick is to have an URLMapping from
RestaurantA to both the page and the folder. 

The solution: Nested lookup calls. By writing a RewriteRule you
can do a nested call to the different mappings so that a call for
RestaurantA.JCBauza.com will grab the RestaurantA part of the URL request, find
from the mappings that a) it is a RESTAURANTREVIEW and b) the page is
RestaurantA.aspx. After that, the nested call will map RESTAURANTREVIEW to the
actual directory it has to go to "/wiki/Restaurants".

The remaining problem: We have 3 files we have to maintain.
Folders.txt is not a huge deal as it won't be changing often, but UrlMap.txt
and Types.txt need to be edited every time you add a new subdomain. Maybe there
is an easier way but for now I think this will take care of having a more
presentable file as well as facilitating changing the path (Folder) were the
files reside with only 1 change (instead of a potentially dangerous find and
replace).

Here is a sample call to the three files:

RewriteRule
.? ${Folders:${Types:%2|}|}${URLMap:%2|search/SearchResults.aspx?q=%2}
[R=301]