To expand on Nick's post.

In the MouseDown event check for the middle mouse button, if it is store the mouse location in a class level var (a Point() ) would work

in the MouseClick event check for middle mouse button, if so get the tab at the location stored in your class level point var and remove that tab (you can also set the tab control to a specific tab, ie the first one or whichever after removing a tab, be sure to check that there's even a tab to go to first)

in the MouseUp event set the class level point var to nothing (to clear it out)