Dedicated "Junk" and "Not Junk" Mail.app buttons?

There's a bug or settings error but I think a workaround would be easier. The bug (not the problem but the reason for the need): I send my gmail through Mail.app and when its spam ends up in the Junk folder, some will be marked by Mail.app as junk and others won't. And if I select all that isn't that should be, with the intent of marking them Junk, one or two will suddenly be marked as junk. I'll wait until no more mail activity showing and unselect those one or two, and suddenly one more will be marked as Junk. And because at least one message is marked as Junk in what I've selected, the button at the top bar says "Not Junk." And I should mention, I get between 50-250 spam messages a day so it's not a trivial thing.

Anyway, the Junk/Not Junk button in Mail is a toggle; if there's a single message selected that's Junk it becomes Not Junk, and sometimes because of the above, becomes Not Junk in the second I go to press it, as it suddenly decided to mark one Junk on its own, then all that Junk is added to my Previous Recipients list, etc.

What I'd really like if it's AppleScriptable or something, is (akin to Unread and Read dedicated buttons), Junk and Not Junk buttons that don't toggle between states. I'd love to select some group of messages, some of which are marked Junk some of which aren't and mark them all Junk with no regard to the prior state of any message. Is this possible to create? I've done very little with, say, AppleScript and don't know if that's even the right tool, but some easy tool to add those buttons would be great.

Thanks for any help!