Branching multiplication of floats

I am trying to modify how real-time Live Link input values are outputted to Metahuman animation.
I want to intensify head roll only to the right (so any Live Link input values below 0 for head roll) I want to multiply by 400.
I am pretty new to Unreal. I thought a simple branch would work. (So; if in range -1 to 0 multiply by 400, else multiply by 1). However, I cannot figure out how to return that float value to then put it into the ‘make rotator’ node as the branch node needs to link an executable action.
Any help would be much appreciated. Attached are photos. They are very messy but I hope you get the idea of what nodes I have been playing around with.
Thanks!