You can replace old_name with either the name of the field you want to replace, or an integer, relating to that field.
I have no doubt I am going about things the wrong way! Unfortunately, I know of no other way.
As an FYI, here is what I'm doing.....
I have a report that refers to 12 monthly fields of current information. As each month passes, the oldest month is moved to another table holding old information. I then add a new month for new information. As the form refers to the 12 specific field names found in the table of current information, I am essentially copying each column of data over one column as a month passes. This way the form can always refer to the same fields and I am essentialy, by changing the name of the fields, moving each field's data into the next month's data.
If there are better ways to do this, I'm all ears.