Oracle Query -Lead/over

I have below query for a single date.

SELECT nsn,thisdate,  
vendor1_code, vendor1_name, qtysum_1, DELIVERED_QTY_1, split_1,
vendor2_code, vendor2_name, qtysum_2, DELIVERED_QTY_2, split_2
FROM 
(SELECT nsn_code AS nsn, vendor_code AS vendor1_code, vendor_name AS vendor1_name, thisdate,
qtysum AS qtysum_1, DELIVERED_QTY AS DELIVERED_QTY_1,
split AS split_1, LEAD(vendor_code) OVER (ORDER BY split) AS vendor2_code,
               LEAD(vendor_name) OVER (ORDER BY split) AS vendor2_name,
               LEAD(qtysum) OVER (ORDER BY split)      AS qtysum_2,
              LEAD(DELIVERED_QTY)OVER (ORDER BY split) AS DELIVERED_QTY_2,
               LEAD(split) OVER (ORDER BY split)       AS split_2
               ,ROW_NUMBER() OVER (ORDER BY split)      rn
          FROM (  SELECT p.NSN_CODE,
                        dv.vendor_code,
                         dv.vendor_name,d.thisdate,
                         SUM(po.quantity) qtysum,
                         sum(po.QTYDELIVERED) as DELIVERED_QTY,
                         rfp.vendor_share_percent AS split
                    FROM fact_po_lines po
                         INNER JOIN dim_product p
                             ON po.dim_product_id = p.dim_product_id 
                         INNER JOIN dim_date d ON po.ORDERED_DATE_ID = d.dim_date_id
                         INNER JOIN fact_pa_item pai
                             ON     po.dim_product_id = pai.dim_product_id
                                AND po.dim_vendor_id = pai.dim_vendor_id
                         INNER JOIN dim_vendor dv ON po.dim_vendor_id = dv.dim_vendor_id
                         INNER JOIN dim_date deff ON pai.dim_date_effective_id = deff.dim_date_id
                         INNER JOIN dim_date dexp ON pai.dim_date_expiration_id = dexp.dim_date_id
                         INNER JOIN dim_product p ON pai.dim_product_id = p.dim_product_id
                         INNER JOIN fact_rfp_product rfp
                             ON     pai.source_rfp_id = rfp.source_rfp_id
                                AND pai.dim_product_id = rfp.dim_product_id
                                AND pai.dim_date_effective_id = rfp.dim_date_create_id
                   WHERE    d.THISDATE = '12-AUG-14'  
                   AND d.thisdate BETWEEN deff.thisdate AND dexp.thisdate
                         and p.NSN_CODE = '2610-01-214-1344'
                GROUP BY p.nsn_code,
                         dv.vendor_code,
                         dv.vendor_name, 
                         d.thisdate,
                         rfp.vendor_share_percent) t)
                        
 WHERE rn = 1
 order by thisdate;

But if I need to do the same for a date range on the order date and have to extract the total sum for a vendor group for that order date range.As in the resultset capture.The bottom section for vendor1 and vendor 2(total order qty,total delivered qty leaving the split) is needed.
Thanks for your time

Please let me know.