Shopping cart workflow restart

Hi,

I have the below requirement for shopping cart.

If the approver changes the cost center at item level, thn I want to restart the workflow.

I am using the Badi u2019 /SAPSRM/BD_WF_PROCESS_RESTARTu2019 . Can anyone tell me which method and how to compare the new cost conter value with old value?

Thanks,

Sivagami R