Creating an automatic report from multiple filtered fields from multiple worksheets

This is my first posting so I apologize in advance if I'm not concise enough.

-I have an excel spreadsheet that I have created with filters. I need to learn how to create a report (perhaps a Pivot Table - which I've never used) that will enable me to compile the total values of certain filtered information(automatically if possible).

-Specific to my spreadsheet (that I'm attaching) I'm needing to report on the total monthly spending by Department (sheet) for Flights, Accommodation and Car Hires for each Job Number.

-First challenge is to use the "Invoiced $ Value" if there is data in that field, if not then to use the "Value on Itinerary".

Second challenge is when travel crosses over the end or beginning of a month and therefore should actually be split.

Thanks Julie