Is there a way to freeze the top (or a section) of a form?

I'm creating a shopping order form where users are allowed to select various products.  I have a calculation widget within the form to show the users the total payment due.  

I would like this calculation field to always appear at the top of the form - but the user can scroll through the items below (similar functionality to any shopping site such as Amazon, Walmart, etc where you can see the number of products within the "Shopping Cart" and the Total amount of $ that is due.

What is the best and simplest way to accomplish this?

Yes, you can use custom CSS code to accomplish this.
This would be the code for your form:

#id_105 {
   position: fixed;
   top: 10px;
   right: 10px;
}

Which would provide the following result:

You can set the top and right values to the ones of your preference.