populate document header text in SES by bapi BAPI_ENTRYSHEET_CREATE

Hi,

I am using BAPI BAPI_ENTRYSHEET_CREATE to create a service entry sheet. But I am not able to populate the document header text (bktxt) in acceptance tab in service entry sheet header in ML81N.

Can anybody help me what I need to pass to this BAPI in order to populate this field.

Thanks,

Mainak