I couldn't tell exactly what you were asking about, but these two solutions should help.
If you are asking how you can make sure that the values in a 2D array are never greater than or less than a user controlled threashold and to set them to those thresholds if they are, look at the Cooerced.png file. This VI will do exactly that.
If you are asking how to find the maximum and minimum values of a 2D array, look at the MinMax.png file. This VI loops through each element in the array and stores the maximum and minimum values in shift registers. The value of these shift registers is compared against each value in the array and updated if the value is greather than or less than the current Max or Min.
Hopefully either or both of these VIs should help you.
