how to transfer actual cost one wbs element to other wbs element

    Hi gurus,

   I have created project and created level 1 wbs element then i book the actual cost for level 1 wbs element.

   Then same project i have created level 2 wbs elements, i want to transfer the actual cost from level one to level 2 wbs elements.

Example : level 1 SS-0000001

                 level 2 SS-0000001-M

   here i have booked the actual cost (PO/FI)  wbs element is SS-0000001, then i want to transfer wbs element level SS-0000001 to level 2 SS-0000001-M.

    i am trying to post through in tcode KB15N but it's asking enter cost element.

please suggest on this process.