Wondering The Best Way To Do This

Here is the
problem that I am trying to solve. We currently have a mail order
manager application that we use. We have several vendors that we have
to initiate purchase orders with, and this is currently done manually.
I am converting it to do the purchase orders through a webservice, but
I would like this to complete in real time. I figured the best way to
do this would be to initiate a trigger when the particular table has a
record inserted. This insert triggers a script, passing the order
number and verifies if a purchase order needs to be initiated based on
what was ordered. If it does, it contacts the webservice, gets the
appropriate data, then updates the appropriate tables with the new
data, all through the script. I have been doing some research, and I
have heard that triggers are simply best to be avoided, and calling
outside scripts could be problematic too. However, I don't see any
other way to do this.