Issue with variable and lerp usage

If I want to interpolate a float to go from 0 to 1, how would I do that? In this setup I want to make a float variable increase to 1.0 after a key press. I have some animation rigged to that variable which then blends using montages. But I am not sure how to set up the variable to increase over time. I think the lerp node is useful for that.

Use a Timeline, with a float going from 0 to 1 and use that as the alpha input.