Well the normal reaction here might be to try using postProcess, possibly wrapping the SearchControls module in a PostProcess module. However while the Sideview SearchControls module implements an export button, it's really just a thin wrapper around Splunk's Export functionality, and unfortunately in the end the exported results are totally unaffected by any postProcess search.
I'll add this to my list of improvements to explore. It would certainly nice to have export still use a given set of search results, but transform it at the last second while it's on its way out.
So to sum up, I think the only way is to submit a whole second search in parallel with the one you're displaying, use the same $foo$ tokens in both, but have the second search hooked up with the SearchControls module, and the first one hooked up to the Table.