Assuming you are on Windows, the free key-remapping product
AutoHotkey
can remap keys and mouse clicks.
For example, the following AutoHotkey script will remap:
Ctrl+Left-click to middle-click:
Ctrl & LButton:: MouseClick, Middle
After installing AutoHotKey, put the above text in a .ahk file and double-click
it to test. You may stop the script by right-click on the green H icon in the
traybar and choosing Exit. To have it run on login, place it in the Startup group at
C:\Users\USER-NAME\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup.