I wonder if this could be done with a third column (true false), which is based on the results of a template that compares the two columns in some way. See
http://manual.calibre-ebook.com/template_lang.html
My skills in this facet of calibre are scratchy at best but I think that's where I'd start experimenting. Templates have several modes of operation - simple, advanced, single function, template program and general program. I suspect you'd need to use one of the program modes.
BR