Insert a new line to F4311 with an existing PO using MBF

Dear All,

I want to insert a new line in F4311 for an existing PO using MBF. I am using Edit line BF for insert but its not happening .

I have tried to change the flag(Insert new line flag set to 1) in both begin doc and edit line .

If anyone have you tried the same scenario , kindly share your thoughts to achieve this .

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Thanks and Regards,