I know you're going to tell me to do this another way but I don't know
how strongly you're going to say it.

I am going away for a few days, and I didnt' expect this. I planned to
put a timer on my kitchen ceiling fixture. The one I used to have worked
fine but failed, and the one after that failed too (after about 15 years
each). The one I bought recently turned out to be no good for CFL's so
I just got another one and it wants the neutral wire.

Only for the current that it needs to run the internal clock. Not much
more than a watch battery puts out, right?

All I've got available is the ground wire. How bad is it to use that
until I can run a neutral wire?.

I already have a 12 or 14 gauge wire running to this box that used to be
used for another purpose, but no time before I go away to scope it out.

The current on that ground will be on every ground wire in your house. Every metal wallplate and every grounded appliance will have that potential current on it. It is possible that you could touch an appliance and a water faucet at the same time and get zapped.

Get yourself some plug in lamp timers. You don't want to create an electrical hazard for your entire household.

John Grabowski
https://www.MrElectrician.TV