Use internal speakers without unplugging headphones?

At work I have a Lenovo X220 in a docking station running Windows 7. I have my headphones plugged in most of the time. Occasionally I want to enable the speakers so a co-worker can hear something. To enable the speakers, I have to physically unplug the headphones. I inevitably forget to plug them back in. When I go to listen to some music, it plays over the spakers and I have to stumble for the mute button.

I want to be able to leave the headphones plugged in at all times so I don't have to constantly reach for the cable. I also want to have some way, perhaps in software, to switch between the headphones and the speakers. Is this even possible? If so, how can I do it?

You can’t. This is controlled in hardware, not software.