FM to delete / clear payment block in Sales Order

Hi,

Could any one tell me the FM to delete payment block in the Sales Order in the Billing Plan. My requirement is, on any given date, if the payment is due, remove the payment block for the sales order. The Payment block value is in FPLT-FAKSP field. But I could not find any FM to change the value of FAKSP to SPACE.

Thanks

Sai Prasad R