Updated value Sales Order

Hi,

I am creating a api that will send the data that is updated in sales order, on whihc trigger i should create my procedure

for example

Order has 3 lines and it is booked

Booking agent adds a new row to order

Now 4 lines on order

I have to send all the lines using API/procedure .

on wich trigger should I execute my procedure(post)

thanks,

7Z