You might have better luck with the responses if you said *exactly* what it is you want to do, not just "run an exe". calibre is not a replacement for the Windows start menu
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If there is some context to the selected row in calibre, explain exactly what it is and maybe we can suggest something. For instance it is possible to do http post/get requests passing metadata from a book using the search the internet plugin. The Open With plugin has the ability to launch based around an attachment or jpg for a book record. If your requirement made sense I could potentially enhance Open With to be slightly less constrained and pass metadata like search the internet does. But I or anyone else is not going to do that unless you say what it is you are trying to achieve to figure out whether it is interesting enough to justify the effort.