How to connect USB hardware to a MBP via an external monitor I have a setup where I am using one external monitor (Dell P2414H) for two laptops - one Macbook Pro and one Dell Latitude E6430. 

The dell is connected via a docking station with VGA cable, and I am able to use the USB keyboard and mouse when they are plugged in to the monitor. 
The Macbook Pro is connected directly to the monitor using a DVI cable and the Mini DisplayPort / DVI adaptor. 

However, my MBP doesn't seem to see the external keyboard and mouse unless I unplug them from the monitor and plug them directly into the laptop.
I need to switch between both laptops very frequently, so replugging is not a good option.

How can I make my MBP see the mouse and keyboard when they are plugged into the monitor?
I think your problem is that USB is not carried over Display Port/DVI. I have an older Apple Cinema Display that has USB ports on it and the cable has both DVI and USB ends that get plugged into the Mac. 

That DELL monitor has an upstream USB port (and I would be very surprised if that is not connected to your docking station for the PC). Connect a cable between that and the Mac and the keyboard and mouse should work.