Alv..handling at new event in ALV

Hi,

I have a problem in ALV. In the report I have to sum up the cols displaying Sales Order and the col displaying P.O #. However while summing for the same sales order there is a one to one correspondence with the P.O

eg . SO # PO #

3301 1000

3301 1000

3301 1000

SO Total = 3 PO Total =3

However I want the PO # count to be 1. I have handeled this in a simple Abap report using the event at new vbeln po cnt = po cnt + 1.

Could you please tell me how to handle this in ALV.

Thanks..