Calculating Angular speed from the current position (deg)

I am sure the solution of my question will be simple, But I don't know why I am struggling with this so much. I have the "Actual_position (deg)" & the "Required_position (deg)". I want to calculate the "Angular_speed (deg/sec)" based on this.

I am doing a simple controller, that it calculated "Delta_position (deg)" = "Required_position" - "Actual_position". Currently I am trying to use the Derivative block to achieve this but with no success. Can anyone tell me where am I going wrong, I kinda feel I have the theory wrong.