How to change Service order quantity using BAPI/FM

Hi All,

Can any body tell me how to change the Service Order quantity (in IW32) using a FM or a BAPI.

I tried using the BAPI: BAPI_ALM_ORDER_MAINTAIN but I am unable to change the quantity. May be I might be missing some parameter. If anybody has done this please let me know the parameters that needs to be passed or if there is any other way out.

Points will be rewarded to useful answers!!

Thanks,

Susanth.