So you basically need to process all cells on the board in a random order, correct?
You can create a single permutation table for all cells.
-> AdvancedRandom: Create permutation with board_size^2 values starting at 0
+ System: For "n" from 0 to board_size^2
-> System: Set randomRow to AdvancedRandom.Permutation( loopindex("n"))%board_size
-> System: Set randomColumn to int(AdvancedRandom.Permutation( loopindex("n"))÷board_size)