Ian, the sheet does both. It has a section that calculates the dimensions, feeds etc needed, then these are converted into g code using formulas such as this:
="G00 X1 Y0 Z"&($H$3+1+C3/2)
The first bit quotes just writes G00 X1 Y0 Z into the cell. The & symbol in Excel concantenates this with what comes afterwards, which is the result of the calculation in the brackets which just contains standard cell references. The result in this case (for certain parameters) is
G00 X1 Y0 Z67.595
I'm cheating here because I've inserted some of the numbers by hand, but in other examples I've done all the numeric values are inserted from other cells in the sheet. So once I've built the sheet I can generate the code for specific dimensions by just changing the parameters. Done things like tapers, cams, crossing out, special pallet profiles for clocks etc.