Database CompoundKey Support for Joomla 2.5

I have a legacy database and I am creating a Joomla 2.5 component to access and manipulate the data in the tables. The JTable of Joomla natively supports an auto-increment "id" field but I need to have a compound-key with up to six fields with different data-types, and none of them as auto-increment. I have also added one table which can be a normal Joomla table with "id" as the primary-key field. I need a Joomla expert to help me with the creation of a class which can select, insert, update and delete records from my legacy db tables while allowing the native Joomla table(s) to function correctly. All custom files and code should be place in the component folders for front and backend support. The Joomla core file should be as free as possible from changes. Please find attached db. If you have done this type of work before I would like to hear from you as soon as possible. Thanks