Niagara Curve Play Rate?

Hi, does anyone have any tips on how to modify a Niagara curve’s play rate at runtime? I’m attempting to build a system where I could set a Spawn Rate that say starts at 100 and curves to 0 over X time - where I can define X at runtime per niagara system that I spawn via BP.

Never did figure this out, but instead drove a float via a BP timeline. Got me where I wanted.