I want to buy a PC and build it by myself. 

I can't buy a monitor now but maybe after 30-40 days from building the PC.

I have a Laptop but it has only **VGA** and **DP** Ports.
There is **DVI** and **HDMI** Ports in the PC mainboard (no external graphics card).

Is it possible to use my Laptop's monitor as my main PC monitor?
Or is there no way but to buy an external Monitor?

I searched but I cant find any thing giving me the answer clearly.

Thanks