This idea comes quite naturally, it would be really nice to be able to put the leftover screens to good use, but in practice it is super complicated. One cannot simply connect the screen cable pins to a vga/dvi plug. Laptop screens are kind of like printers, there is not a common hardware standard and what translates the signal from ex vga to what you see on the screen is done somewhere on the graphic card.
Google a bit - there are people who have done it, but it requires buying a circuitboard that processes the signal from vga/dvi, and again that circuit has to be made for that specific screen.