Mapping Logic to be created.

Dear Experts,

I have a simple requirement to develop mapping logic such as,

Source Structure

-Header

  - Item                        (1...n)

    - Field1

    - Field2

    - LineItemNo

    - Field4

Target Structure

-Header

  - Item                         (1...n)

    - LineItemNo1

    - Field1                     (1...n)

       - sub_field1

       - LineItemNo2

I want to mapLineItemNo from source to 2 location at target field which are at different levels.P.S. for a particular ItemItemNo in source the LineItemNo1 and LineItemNo2 should be same in target structure.

Kindly advice.

Regards,