Disable button in SUS Portal

Hi,

I am working on SRM 7.0 project and I was asked to disable 'Reject all' button in purchase order item details screen of Supplier self service (SUS) portal.

Navigation: log into SUS portal -> Orders -> New -> Double click on PO number -> click on 'Process' Button

SUS portal is based on BSP and I have gone through the respective BSP page and view. But I dont know how to proceed as I am new to BSP technology. I would be thankful if any body help me on this.

Regards,

Krishnam