For some customers specific requirement, a custom column can be designed that will use the "Nested If" functionality for giving desired results.

For Example :
   This customers requirement is to be able to bill hours entered in UDF (VehicleHours) based on the vehicle number chosen in another UDF (VehicleName). The Custom column can be designed as such :

If(VehicleName="JD 6420",VehicleHours*65,If(VehicleName="JD 4720",VehicleHours*45,If(VehicleName="JD 6430",VehicleHours*65,0)))

 The above formula will will check for vehicle name (JD 6420) and multiply the hours entered in that field of VehicleHours by the value given (65) if it is true, or else it will enter the nested if function to check for the next value. If no 'VehicleName' is matched, the function will throw '0' as an answer.
  The key point to note is that in the above formula, all arguments should return 'Number' or 'String' Value. The formula will not work if one argument returns 'Number' and the other returns 'String'