I do all the time. I let a pound of butter come to room temperature, then put it into my mixer with a whisk attachment. Whisk until fluffy and gradually add 2/3 cup canola oil and whip until it's completely incorporated. Scrape into an airtight container - like Tupperware - and refrigerate. Before I need to use the whipped butter I take it out of the refrigerator for a few minutes to allow it to soften a bit. Spreads just like the stuff in the store and a lot less expensive.
I've used both salted and unsalted butter and am not sure which one I prefer. Depends on what I'm spreading it on.
"As a girl I had zero interest in the stove." - Julia Child
This is real inspiration. Look what Julia became!