Compare how close values are

[SKETCHwade]

I have 3 columns, Next service, Last service and current hours.
These are all in hours format, an example would be next service 1750, last service 1500, current hours 1680.

I would like to make an expression to result in the number that was closest to current. In the example above it should return 1750.

Any ideas on how to do this?