Sadly, there's no way to adjust anything on the switch. Not sure how I'd check the refresh rate, but since the Xbox works ok throught the switch, and both sources work ok when connected directly, I'm guessing that it should already be ok?
Thanks for your response budwich. I'm only using 1380p or thereabouts. I'm guessing that the switch I have is limited to 1080p - the monitor handles it perfectly when connected directly, but unfortunately only has one HDMI port. I'm considering trying to find a switch that explicitly states it...
I got a HDMI switch to connect my laptop and xbox to a monitor via the only HDMI port on the monitor - the switch detects both sources but only displays the xbox. Both sources connect to the monitor perfectly without the switch. I can't adjust the laptop display down to 1080p (who'd want to do...