ALV PROBLEM

Hi,

Suppose I have the arrangement like this

In header

prog xyz

toatl amout

total order

sales type s.org. amout(netpr) total order

x 1000 1200 25

y 1000 1500 30

Now my question is to how to sum up all the amout & order & print it into herder in row total amout.

Will u tell me how to use this logic in alv. My output table is itab.