So without getting into hacking around in the XML, you'll need to first switch the data source, by using "Edit Data Source" (if the source is the same...eg. Excel to Excel), or will need to bring in the new datasource and then choose "Replace Data Source" (From the data top menu) if it's a different type (eg. Excel to MS SQL).
This will get you part way, but as he column names are different everything will break...you can then use "Replace Reference" column by column, to replace A with AA (for example)
Ideally you'd have the same column names in both sources, then you can just use the options above.
I've attached a .gif showing the replace reference process.
Hope that helps
DataSource SwitchGIF.gif 876.6 KB
This is what I was looking for Simon. Thank You.