My Garage - possible to have negative cost?

[sjg]

There seems to be some validation on costs that get entered and it won't allow a negative value. It would be handy to allow it - especially as some costs can cover more time than the car is owned for. On selling a car, it would be handy to be able to enter a negative entry for tax/insurance so that the final figures show the actual costs for the period it was owned for. At the moment you'd have to fudge it by editing the original entry to show the part-year cost.