HMA ATR Range

In Alan's books he talks about his 'range indicator' which is the HMA and ATR to give buy / hold / sell signals. This is my version as he doesnt give the formula.
It is the HMA with the ATR added and subtracted and plotted above & below the HMA to create a range.
According to Alan's terminology: HMA = Central Cord, SL = Lower deviation, TP = Upper deviation