Since you are requesting a custom watchlist column to add to the scan results section I have moved this out of the "Stock Scanners" topic and into the "Watch Lists" topic. I have also updated the title of the question to more clearly describe the context of your request.
I have learned to avoid using the "fold" looping structure because it's limitations make it extremely difficult to apply to anything useful. It also introduces extra load on the script because the loop will run each time the chart is updated.
Here is my generic solution which includes two moving averages. The code displays minus 1 of no crossing below event is found. Once the crossing below event occurs it immediately tracks the lowest price until the moving averages cross back in the other direction. The recursive variable will then hold onto to that value (lowest low between crosses) until a new crossing below event occurs. At which point the cycle repeats.
def maOne = Average(close, 50);
def maTwo = Average(close, 200);
def crossBelow = maOne crosses below maTwo;
rec lowestBetweenCross = CompoundValue(1, if crossBelow then low else if maOne < maTwo and low > 0 and low < lowestBetweenCross then low else if maOne > maTwo then lowestBetweenCross else lowestBetweenCross, -1);
plot data = lowestBetweenCross;