BAPI to update Material planning in networks: primary costs on PS Activity

Is there a bapi or function module that allows you to update the Material planning field on a network activity (AFVGD-MAT_PRKST) ?  I can read the data with BAPI_BUS2002_ACT_GETDATA  in BAPI_BUS2002_ACT_DETAIL but the field does not appear in BAPI_BUS2002_ACT_CHG.