The original spreadsheets dealt with two aspects of the plan: gear, and operating costs. Gear included things like clothing, entertainment, field equipment, and such. Operating costs included things like tuition, living expenses, the cost of keeping things like my mobile phone and car insurance paid for back home, flights, and the like. Excel was great because I could plug in a couple of simple scripts, like a cascading cell system that allowed me to easily account for changes in the exchange rate between the dollar and the British pound.
My spreadsheets for Operation Highlander were copied and retooled for my sojourn to the Middle East, which was a good pre-Highlander exercise. I've since used Excel to come up with a variety of additional spreadsheets to help me through the process of preparing for Scotland.
I've already posted a few of my spreadsheets, and as appropriate, I'll post more as time goes on. Stay tuned to learn more about the trip and how I've planned for it.