#include <array.au3>
Local $array[3] = [123, 321, 456]
For $i = 0 To 2
If _CheckNum($array[$i], 6) Then $array[$i] = ''
Next
_ArrayDisplay($array, 'The Result')
Func _CheckNum($num, $sum)
If Not StringIsDigit($num) Then Return False
If StringLen($num) <> 3 Then Return False
Local $x = StringLeft($num, 1)
Local $y = StringMid($num, 2, 1)
Local $z = StringRight($num, 1)
If $x + $y + $z = $sum Then Return True
EndFunc