Is it possible to update XMLMap's schema?

[William]

Using automation (C#), I created a XMLMap using a schema and mapped
all relevant elements to some XML-Lists. However, is it possible, or
how to update the schema elements without lost of formatting?

For example, if the schema had been updated to include an extra column
at the end, how can I (or is it possible to) insert this extra column
onto the existing XMLMap/Schema?

- I can't remove the existing XMLMap and insert a new one since this
will causes all format associated with XMLList to be removed.

- I tried accessing the XMLMap properties, like XMLSchemas collection
and the XML properties, but all are read-only.

Thanks in advance for your help.
William.