Hi Suresh
As you have told your " This freight carrier is a internal company"...So you do not want to charge it separately by FI entry. Now In costing sheet you can define a line as "Freight Cost" and Rate will be based on material cost already booked in the accounts or some other Base Value. In this way you can calculate one Freight Cost as OH charge in cost estimate where no further FI entry will be generated.
What is your doubt .." it dont think it would be possible with costing sheet." explain
Kamal