How to activate motion blur while the player dashes?

I am working on an indie game and me and my team are in pre production. I am starting to put together a test build for testing the game mechanics. I have a question: How to activate motion blur while the player dashes?

When the player gets a DASH powerup, when the player presses the key bind to dashing, they do a DASH power. During the time period of Dashing, I want the screen to have a motion blur not all over the screen, but only around the outside of the middle of the screen. so there is an invisible circle around where the player is on the screen, I want the motion blur to happen OUTSIDE of it.