I just thought of a way but I will need your feedback.

I am thinking about creating an if statement to display:
Shopping cart is empty
sub-total: $0.00
shipping: $0.00
total: $0.00

and once a customer add product I can display the result from your mod. I am looking at the sidebox code which part of the code will I need to copy in the if statement, also I want to style the result, what is the shortest way to do it. I want it to be displayed all the time so I will not care much about the admin control.