Is it possible to use a float value as the starting input on a timeline?

I’m working on a deceleration value to add movement to the character without changing the deceleration and ground friction in CharacterMovement (to avoid sliding around while running). The timeline I’ve made works just fine, but I can’t see a way to use a float value as the starting point (so that instead of starting at 1, it always starts with the current speed value anywhere between 0 to 1). Is there another node that might achieve this, or will it be necessary to create a separate function to alter the speed value over time?