I don't really understand what you mean by "a complete high/low", I took it as a whole bar. Nevertheless this is what I came up with:
[Opening Point of the Position]
Bar Opening
Enter the market at the beginning of the bar
Base price - Open
[Opening Logic Condition]
Moving Averages Crossover
[ A ] The Fast MA crosses the Slow MA upward
Base price - Close
Fast MA method - Simple
Slow MA method - Simple
Fast MA period - 3
Slow MA period - 50
Fast MA shift - 0
Slow MA shift - 0
Use previous bar value - Yes
[Opening Logic Condition]
Moving Average
[ A ] The bar opens above the Moving Average
Smoothing method - Simple
Base price - Low
Period - 50
Shift - 0
Use previous bar value - Yes
[Closing Point of the Position]
Bar Closing
Exit the market at the end of the bar
Base price - Close
[Closing Logic Condition]
Moving Averages Crossover
[ a ] The Fast MA crosses the Slow MA downward
Base price - Close
Fast MA method - Simple
Slow MA method - Simple
Fast MA period - 3
Slow MA period - 25
Fast MA shift - 0
Slow MA shift - 0
Use previous bar value - No
Again, if I understood you correctly, the strat above buys like you stated, so to make it behave correctly for sells, logical groups should be involved. Final version then:
[Opening Point of the Position]
Bar Opening
Enter the market at the beginning of the bar
Base price - Open
[Opening Logic Condition]
Moving Averages Crossover
[All] The Fast MA crosses the Slow MA upward
Base price - Close
Fast MA method - Simple
Slow MA method - Simple
Fast MA period - 3
Slow MA period - 50
Fast MA shift - 0
Slow MA shift - 0
Use previous bar value - Yes
[Opening Logic Condition]
Moving Average
[ B ] The bar opens above the Moving Average
Smoothing method - Simple
Base price - High
Period - 50
Shift - 0
Use previous bar value - Yes
[Opening Logic Condition]
Long or Short
[ B ] Open short positions only
[Opening Logic Condition]
Long or Short
[ A ] Open long positions only
[Opening Logic Condition]
Moving Average
[ A ] The bar opens above the Moving Average
Smoothing method - Simple
Base price - Low
Period - 50
Shift - 0
Use previous bar value - Yes
As you can see I tuned the indis to fit your strat, the best I can achieve without custom indis unfortunately.