Export multiple sheets to XML
 

I'm trying to export multiple sheets with the same type data in each
sheet to XML. I can map field in one sheet to a schema and then export
to XML, but I need to get the data from all sheets with each sheet's
data in a separate major XML element so I know which sheet it came from.

After mapping the field in one sheet to a schema, I can't map the data
field in any of the other sheets because it is "already mapped". But
when I export I only get the data from one sheet.

How can I export all sheets to XML?

Thanks.