BDC not able to change Sales order no using Tcode VA02

Hi All,

I need to change Sales order schedule line delivery block using bdc I have created the BDC Program using session method and its working fine, but when i need to change multiple SO's the sales order no is not changing ie for each itreation SO No remains same. I have even checked the BDCDATA table also its also has all my sales orders. WHen i execute this session its only taking First sales order and repeating.