Since you're asking for help....
1.) You'll need a database (to make this easier on you) to track hair-cuts, prices, users, etc.
2.) You'll need to know how to use AJAX (or one of the libraries like jQuery or Prototype) to call a php script to add up the values and apply any discounts and such
3.) You'll need to know how to use Javascript to create the "subtotal" on-the-fly at the bottom.
If I were going to do this, I'd start with the database. From what you say, I can see 4 tables off the bat:
[indent]i.) Haircuts
ii.) Prices
iii.) Users (for administrative purposes)
iv.) HaircutPrice (to map Prices to Haircuts)[/indent]
Now, you could use two tables (one for users, the other for haircuts); however, by splitting the price(s) from the haircuts table, you can have multiple haircuts with one price and if you raise it, they all get raised.
From there, I'd work on the PHP side to make the form show up and display the check-boxes as I want with the correct values. Then I'd work on the javascript to create a sub-total for the selected items.
Once I have that, I'd work on the PHP to actually take the submitted form and sum up the cost, apply discounts & special rates, and add tax (if any). I'd return that either as JSON (PHP 5 suggested) or XML.
From here I'd look at the AJAX library I want to use and look at how to call my php script to come up with a total and update the proper area on the page.
Finally, I'd work on the administration section with a login section, and a haircut and price modification section.
Hope that helps. If you were looking for someone to code it for you, you came to the wrong place. If you would like help writing it, come up with some basic code and design ideas, and we'll help you out as you need it.
