How to get PR's delivery schedule data?

Hi,

Please help as subject. Because I want to using 'BAPI_REQUISITION_CHANGE' to change PR data.

I know to call function 'BAPI_REQUISITION_GETITEMSREL' to get PR detail, but this function can't getting PR delivery schedule's data. We using SAP AFS and we PR data will including the grid value.

So, I need to know that how to get PR delivery schedule data to update PR.

Thanks a lot for help.

Best Regards,

Nicole Chen