Hey try this one:
http://www.usd.edu/trio/tut/excel/
If ye know how to use other programs like Word or Access, you should have no problem giving yerself a crash course in Excel. I'm an IT teacher and it is one of the easiest programs to teach, everyone seems to pick it up easy if they already know one or two other programs. It is very straight forward. Best of luck with the interview... Just get a few hours practice in and bluff your way through :D
Keep us posted in how it goes...
Misfit