Dual display with MacBook Pro (13-inch, Mid 2012)
Your Mac technically can only support it's own internal display and one external display.  However, there is a "hack" that you can use to get a 3rd screen (2nd external monitor)

What you will need:


mini Display Port to DVI cable/adapter
USB to DVI adapter


There's a YouTube video with someone using this method with 3 external monitors (total of 4 screens) so this is entirely doable.  Keep in mind that the bandwidth on USB is nowhere near the bandwidth of DisplayPort so there will be some lag when it comes to intensive video type applications.  In other words, don't expect excellent results if you are gaming.