BAPI Sales Order create with reference Invoice document

Hi

  I am using BAPI ''SD_SALESDOCUMENT_CREATE''  to create debit memo request with reference Invoice document.

  First time its successfully created with reference Invoice.When i am going to create 2nd time debit memo request with  same reference Invoice and item

  no its giving following error.

       Error in SALES_ITEM_IN 000010

       Condition ZSLS is not allowed as header condition

       Sales document  was not changed

    Please help any one to resolved this issue.

   Regards

   Shyam