Purchase orders created from Equipment work order - Approval part

Hi,

I am working in CAM module. I am creating a purchase order from Equipment work order screen.

I have observed that when I create a PO from parts TAB of WO, then the header branch plant of PO is defaulted as Branch defined in Equipment master (even if we override the branch plant on the detail line of Part list screen.)

Now, I want the detail level branch plant defined in equipment part list to be populated as header level branch plant of PO.

This will enable me to setup approval level based on the equipment cost centre.
can you please guide me in the same.