SQL & PL/SQL

I am using PL/SQL to import data from a datawarehouse. I need to link one of the colums in tables A to another column in Table B. The column is indexed in table A, but it is not indexed in Table B. As a result, since there are many many records, it is very slow in pulling the data. Figured if both were indexed this would be sped up..

I have no direct control over the tables in this datawarehouse. i just connect to the DW and query the tables..Is there anyway to tell PL/SQL to index the non-indexed field I have to link to, via perhaps a function or some other way. I wouldn't think this is possible, but am fairly new to this sort of thing, so thought I might double check..

Thanks for any assistance..