How do I make particles slow down along their movement path over time?

Imagine I have particles that fly out along, say a 45 degree angle at a speed of, I guess 5. No gravity. So they just linearly travel along this line. I'd like them to slow over their lifetime or just over time down to a value (in my current case, that would be 0). That way I could have them burst out very fast but then quickly slow down to 0 soon after. I've tried messing with the velocity over time stuff but it doesn't do what I want it to do. It's literally modifying the velocity, so a particle may wind up taking a different path altogether. I'm launching particles at random angles and speeds (with no gravity in this case) and just want them to slow down over time. Is this possible? Am I missing something right in my face? And if not, is there a way I can extend the particle editor? Thanks!