How to temporarily exclude a folder from a search

I often use spotlight to locate documents quickly. The one annoying thing is that I often email documents to share them and spotlight will find the version of the document indexed in my mailbox attachments folders. Is there any way to selectively exclude certain directories while searching? I'm thinking something along the lines of:

http://macosx.com/forums/howto-faqs/225786-advanced-spotlight-features.html

I'd love a "not:message" operator or something.

I don't want to tell spotlight not to index any of my email–it's useful and sometimes I search for "kind:message". The only way around it I see would be to drag all of the "Attachments" subfolders under all of my .imapmbox folders (I'm using gmail imap). Anyone know of an easier way to do it?

Thanks.