Swap your right-button ＆ middle-button's actions.
If you have Microsoft mouse, its bundled software IntelliPoint can easily do that. Just go to Control Panel, find the mouse icon.
You can also use AutoHotkey.
; AutoHotkey code to swap middle and right buttons $RButton::MButton $MButton::RButton
Create this file, save it as
swap_buttons.ahk, and you need to tell AutoHotkey to start it when your computer starts. For how, see: AutoHotkey Tutorial.
Also, most gaming mouse have programable buttons that lets you swap buttons. Once set, you can plug the mouse into any computer and have your own keys. See: Xah's Computer Mouse Guide.
Why do you want to swap the buttons?
Linux: How to Swap Mouse Buttons.