Use the Old Value Argument field to map a mobile business object(MBO) parameter to a second (old) argument.
Use the Old value argument field to change an Update operation's parameter from its current value to a new value, while still allowing access to the parameter through the previously defined argument. For example, if you use the Update operation of an MBO to modify the lname parameter's argument from Jones to Smith, the Argument value is Smith, and if you choose to, you can map the Old value argument to Jones.
The old value is available from a drop down list, in the form sup_oldvalue_argument_name (where argument_name is the name of the original argument, lname in the above example. The Un-map option unmaps the old value.