VFX graph using curves (or similar) to drive variables

Hello, I'm using "periodic total time" to animate rising and falling turbulence in the "update particle" module. However, this takes a value from the first number to the second, then snaps back to the first. What would be the recomended way of animating a variable so that it looped, or even ping-ponged? I tried to plug in a curve, but it doesn't seem to take that as an input.

 

You can create a sample curve node and input your periodic time to the time parameter.