...only once while a strategy condition it true? (Wait for the condition to be false and then take action only once when the condition turns true again.)

Untested but try something like this:

 

Code

#region Variables privatebool myFlag = false; // Default setting for MyFlag #endregion protectedoverridevoid Initialize() { CalculateOnBarClose = true; } protectedoverridevoid OnBarUpdate() { if (historical) return; if (Close[0] > Close [1] && myFlag == false) { Print(DateTime.Now + " It's going up!"); myFlag = true; } else myFlag = false; }

That should work nicely.