How to Make Branching Spline Paths with Collision?

So my character moves along a spline in a sidescroller fashion. I’m trying to figure out how to make the character switch to another spline path by colliding with a box collision. If you look at the images below, right now, my character can move down Spline Main just fine. But I’m having trouble figuring out how to make the switch in the character’s BP to Spline A or B.

I’m mainly an artist and I just started using UE4 like last week, so my blueprint is really just a replicate of a tutorial. I asked the tutorial author what he would do to make branching paths. He suggested leaving SplineReference(which is the variable type Spline Main) as is, and adding more code that sets the SplineReference to the value of Spline A, B, C, etc. I spent two days researching and toying with it to no avail.

Right now, the Spline A/B BPs have nothing in them because I’m not even sure how to make the Component Event Overlap for the box collision check and switch to another spline path.

TL;DR: So,basically, my problem is twofold–how to make SplineReference variable switch to other splines so I can move off to other paths and back to Spline Main, and how to make the collision box detect it and make the switch.