Velocity

I want to create an indicator that tells me how recently a stock is making new highs (or lows) with a plot showing me when the direction has changed.

If I use a 20 bar lookback, I want it to look something like this for Highs:
(Num Periods - Num Periods since Highest High / Num Periods) x 100

Similar for Lows:
(Num Periods - Num Periods since Lowest Low / Num Periods) x 100

Then I want to plot the 2 indicators with an alert when they cross over each other.

Thanks if anyone can help with this.