Hello walkinginspace,
You should take a look at Material Parameter Collections in the documentation: Material Parameter Collections | Unreal Engine Documentation. Through the use of this page, you’ll be able to create a parameter collection, which in your case would only include your emissive strength parameter. The blueprint shown in the tutorial will need to be modified a bit. I was able to get my material to glow by using an OnActorBeginOverlap on a nearby box trigger and then using a set scalar parameter node to set the emissive strength parameter to 100. Then OnActorEndOverlap, I set the scalar parameter value back to 0 to stop it from glowing when the player exits the trigger. I hope that this information is helpful!
Have a great day,
Sean Flint