Cropping pages using a hotkey

I produce PDFs where I work that have both A- and B-size pages (i.e., letter and tabloid). When we first produce the PDF, all pages are B-size. We have to go through and crop A-size pages to 8.5" from the right. I'd like to be able to just press a hotkey that would crop a single page or set of selected pages to 8.5" without going through the Crop Pages dialog. I've tried creating a Custom Action to do this but there's no option for selected pages; it only allows a specific page, page range, or all pages to be cropped. It also has no options to assign a hotkey. We have Evermap, so that's available to us if that's a good option to create this tool.

I would be thrilled if we could create a tool that would crop the pages automatically. The right hand side of pages that need to be cropped have no content whatsoever. If there was a tool that could detect that and crop the page to 8.5" from the right automatically, that would be a massive bonus. But I'd be happy with having a hotkey and doing it as I requested above.

I have little experience with scripting, so I can't create one of my own. I'd be happy with whatever method (JavaScript, Action Wizard, etc.) is needed to achieve this. Thanks for any help.