IDOC Posting with new fields in VA01

Hi,

Previously i asked for creating New fields in VA01 screen.

i got that now i need to create a sales order based on the Inbound IDOC which i get and i will be getting new fields which are created .

And this Fields data is coming from an Extension to the Standard IDOC. Sales order is getting created but the new fields are not getting populated nor stored in VBAK Table.

pls let me know why is this.And provide me with a soultion.

MG.