Recently purchased by another company that uses Cognos - Chart of Accounts is different

I have a question that I hope someone can help me with.   My company was recently purchased by a larger company that is not using Oracle (they use Cognos) and they have a different chart of accounts than us.  They would like for us to be able to map our accounts to theirs, and have the ability to generate Report Writer reports with either set of accounts.  We are currently setup as:

Segment1 (2) = Company Code

Segment2 (3) = Not used, always zeros (avaible for possible future needs)

Segment3 (4) = Product Line

Segment4 (5) = Account Number

Segment5 (3) = Department

All that our parent company cares about is segment1 and segment4, the company and account numbers.  We would need to *rollup* our current breakdowns by product line and department.