How to get Work Order material serial number

Hi Guys,

             I am trying to get Serial number of a work order component ,material.

I try using GET_SERNOS_OF_DOCUMENT.

passing KEY_DATA-TASER = 'SER05'.

                               PPAUFNR = <Work order No.>

                               PPPO = <item>

but it's not bringing any results.

any help..?

Thanks

Sam