I got the fuel calc working in Diaftias mod. It was not easy! You are missing a whole bunch of steps. My suggestion to you is to go through the UI files in the 'Common' folder of my mod and make the changes that you see needed in your mod with regards to the fuel calculator. There are too many scripts to post to get this working, you have to do the leg work. You also need a bmpOk so all the referenced codes are in your coomon ui folder. I will examdiff each file and see what differs. Thanks for the advice.
Also in the '800_480/UI' folder. It took me several hours going through all the code for the map changer and the fuel calculator, and a LOT of error messages. Error messages are good though, because you know where the problem is in most cases. In Diaftias mod that I redone, I added probably about 60-100 new lines of text, most of it to incorporate the mapchanger and fuel calculator.
I did added the map changer about a month ago. I got that working fine. Let me know what steps you took to get the \fuel calculator going. I also spent hours going over the files in the common/ui.
Thanks
Jimbo