Variable field name in update_recordSet

Is it possible to use a variable to specify which fields to update in a table with the update_recordSet?

I have a table with sixty different fields in which all records in specific fields will need to be cleared out each month, but each month, different fields will need to be cleared out.  Can I use a variable to specify which fields?

Something along the lines of:

    str     fieldName

    fieldName = 'JanuaryOnlineSales';

    update_recordSet    myTable

    setting

        fieldName = 0;