Thanks littlevoices, great calculator and a great piece of programming.
I have a query/tip about the calculator and multi-legs which threw me until I split up a multi-part journey. What I did was to enter the following legs on the same sheet (as one-way):
1) LHR HKG NZ Business (ie. a stop over here for a few days)
2) HKG AKL NZ Business
3) AKL LHR NZ Business (and coming all the way back in one go)
Doing this you only get a total expenditure of 6,750 miles which is far too few. Omitting Line 3 will give you the right total on the way out and to get the return total you simply have to do another sheet with the return leg by itself. Not sure what's going on but I thought I'd share it with you and anyone else incase they faced something similar.
Thanks again! ^