Parts Requirement HTML

Hi All,
We are creating parts requirement and want to use IR-ISO.
The Source Org (A) and Destination Org (B) are in different OU, we are creating parts requirement in Destination Org (B), the IR is being created correctly in B where as the ISO is also being created in B which is wrong. The ISO should be created in created in Source Org (A).
In Parts Requirement HTML the source org is entered along with its order type to be used, but the system is automatically taking the ISO order type from Destination Org (B) from purchasing options.
How can this be rectified.