Dynamically adding invoice amounts to columns with monthly headers

I am building a template for a report that will print out a list of circuits. For each circuit in the report we want to show the cost of the circuit for each month we have an invoice for that circuit. In other words, there can be many invoices associated with one circuit, and we want all the invoices within a certain date range to show on the same row as the circuit. To help clarify, the structure of the xml data will be as follows:
<?xml version="1.0" encoding="UTF-8"?>
     <Invoice>
          <Invoice Amount>
         <CIrcuit Id>
        <Invoice Month>
     </Invoice>
So on an so forth. In our template we want: