Behind the scenes, the script monitors the Outlook window for a middle-click (which on some ... re about to fall in love with AutoHotkey–and your middle mouse button.

Many laptops will simulate a middle click if you press the left ... you can always use an app like AutoHotkey to map the middle mouse button to just about any action you want.

Even if I need AutoHotkey ... Open the Synapse app. Click the tab for the device you want to modify. Select the button you want to program. From the dropdown menu, select Launch Program.