How do I control which applications receive mouse input? On Windows I have been using X-Mouse Button Control to control which applications receive mouse input. I need to know how to do this on a Mac.

Specifically I am using Mumble and want to bind the "back" button on the mouse to Push To Talk globally. It must have no action in any other application.

I'm using an MMO 7 mouse. But sadly the software that comes with it does not have this functionality.
I have used USBOverdrive in the past with Logitech gaming mice. ( Not for gaming but the number of buttons)

The app gave me control over what buttons would trigger when in different apps. It has global options also.


  The USB Overdrive is a device driver for Mac OS X that handles any USB mouse / trackball / joystick / gamepad / media keyboard and any Bluetooth mouse from any manufacturer and lets you configure them either globally or on a per-application, per-device basis. Note that the Apple Magic Mouse and Magic Trackpad are not handled by the USB Overdrive to let Mac OS X implement its full multitouch support.
  
  The USB Overdrive reads all kinds of wheels, buttons, switches and
  controls and assigns them to useful actions like clicking, typing,
  scrolling, launching, opening documents and so forth. It can easily
  handle several USB devices at once and can assign different settings
  to each one.
  
  The USB Overdrive works in Mac OS X 10.6 (Snow Leopard), 10.7 (Lion)
  and 10.8 (Mountain Lion) in both 32-bit and 64-bit modes. Users of
  previous Mac OS X releases should stick with version 3.0.1 of the USB
  Overdrive.