Issue with Incoterm1 of Header using BAPI_CUSTOMERCONTRACT_CHANGE

Hello Gurus,

I am new to BAPI's and this is first time I am using BAPI.

My requirement is to changes incoterm1 value in the header from say AAA to BBB.

Could anyone please help me how can I achieve that using BAPI 'BAPI_CUSTOMERCONTRACT_CHANGE'.

I tried by give following inputs to BAPI in SE37.

SALESDOCUMENT - Contract Number

CONTRACT_HEADER_IN-INCOTERMS1 = 'BBB'.

CONTRACT_HEADER_INX-UPDATEFLAG = 'X'.

CONTRACT_HEADER_INX-INCOTERMS1 = 'X'.

But it is throwing following Error in RETURN Parameter -

T ID  NUM MESSAGE

E 00   347 Field header_inx-updateflagX is not an input field.

Please help me

Thanks,

Mayur