For Buy checking, you could use "Price x> Indicator" for "Market Properties" "Highest Price (Candles Period)" Start Candle =1 and End Candle = Constant (so you can vary it) Get "Price Value"
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Then opposite for Sells - Lowest Price...
This performs the same function as the Donchian Price Channels indicator (per the original Turtles).
The standard Turtle approach is to find the Highest/Lowest Price (end candle) in the last 55 candles (was daily in their settings), so this helps with not getting in before the trend (or "run") has established.
So play with the End Candle setting til you get a value you are happy with.