dell L502X Choosing between Intel HD Graphics and NVIDIA 540M

Hi Everyone

I have a question regarding the two graphics options. I've currently got two monitors connected to my dell L502x. One through the HDMI and one through the display port. Ive got one of them set up horizontally for regular use and the other one set up in portrait mode for reading documents. When I checked out the setting however I noticed that the HD Graphics was powering both the laptop screen and one of the monitors while the NVIDIA 540M was powering the other external monitor. Is there any way to change this so that the 540M is powering more than one display? If not, is there any way to assign that card to the laptop screen? If it has to be one of the external monitors which monitor do you think I should assign the 540M to?

Thanks