Downsampling an external monitor on a Macbook Pro

I was wondering if anyone has succeeded in downsampling an external monitor for a Macbook Pro. I currently have a late 2013 Macbook Pro (Retina) with Intel Iris Pro 5200 graphics card.

I just bought a Dell S2740L monitor and I realized it only goes up to 1080p :(

I found that I can downsample the monitor to 1440p but the Intel drivers only work on Windows. If anyone knows how to downsample the monitor on a Macbook Pro that would be really helpful!