How to Make Camera "Peek"?

I have a camera on a springarm that follows the character, but it’s difficult to see what is directly in front of them. I would like to implement something that allows the camera to pan down a bit using the mouse (“peeking”). Like making the mouse move the camera a specific distance on the XY axis if it goes near the edge of the screen. How would I got about doing this? I’ve included a pic for reference.