How to add shipping charge to sales invoice

[Charley Tiggs <..hidden..>]

I've successfully created a sales order and created an invoice. 
Tonight, I realized that I had no way to enter the shipping charges.

The client has graduated shipping charges depending on the total of your 
order.  For example:

<= Point A = 5.00
<= Point B = 10.00
<= Point C = 15.00
 > Point C = 25.00

How would I handle this within LSMB?  I tried creating multiple services 
with the account being the shipping & handling account.  But when I go 
in to create a sales order, I still don't get the option to enter a 
shipping charge.  How can I get a field for shipping charges to show up?

Charley