Data Structure array/Lookup questions

I am creating a module whose goal is to summarize around 200k records
(current month) from a file with around 13mil records, into company totals
(around 64 groups).  To save time, I have written an LF sorted by date,
descending, and as I iterate through the file, as soon as I reach a date
before the current month, the loop concludes.  

During this iteration, I would like to summarize each record into a data
structure array (around 64 elements), with one element for each company.
This will avoid iteration through a summary file of the 200k records.  

The questions I have (which I was going to save for the Chicago RPGWorld,
but I can't wait) are as follows:

First of all, can I somehow DIM the data structure array based on the number
of records in the company file?  This way, if we add companies, I won't have
to modify and re-compile.  Also, I won't have to make a guess-timate of
around 150, and dimension unneeded elements.  

Then, if the array elements contain a 3-alpha and a 11,2-packed field, can I
use the %Lookup BIF to lookup the 3-alpha identifier for each company as I
am summarizing?  Will the other data structure field interfere with this?  


Tony Carolla
MedAmerica Billing Services, Inc.