Role Back error

I using Nav 4.0SP3 HF6.I am creating Subcontracting order by using Subconworksheet if any type of error comes while pressing button Carry out Action Msg to create subcontracting order then in subcotracting purchase header fills and Puchase line is empty.If any type of error comes the system should role back(Means Purchase header should not be created).I am using Requistion worksheet also to create Purchase order transfer order also.I saw the code in Codeunit 333 there is commit function used in Function "Insertheader".If I comment this code then System role back if any error comes while creating Subcon it is running all right but I cant comment this commit code because I am also using Requistion Worksheet.What I have to do?