Any way to modify field's OptionString ?

Just wondering if there is some way to modify field’s Option String from C/AL. I want to make a function to change the field’s number assuming there is data in the field. For this to be done I need to create a new field (using table Field), copy all the data to the new field and remove the old field. Works fine with Integer,Code,Decimal,Text… but if the field is of type Option I just cannot find a way to access its Option String property (which can be shown in Object Designer when editing a table), but table Field just doesn’t have that field…? Any ideas? Another idea from my side would be to handle Option type fields as Integers and create a new field with type Int, transfer all data to it, empty the old field and do MODIFY on original Field record and after that transfer the data back, which involves one extra looping through the table…

Yes, tried it the other way:

        tr@1000000005 : Record 2000000041; // Field
      tr.GET(tableNo, fldNo);
      tr.RENAME(tableNo, newFldNo);

This won’t work, error is ‘You must specify the property OptionString for the SomeField field.’ Field fldNo is of type Option. Works fine with other types… Any ideas?