Local $text = 'your text to replace1234!@#$%'
Local $array = StringRegExp(StringLower($text), '[a-zA-Z0-9%]', 3)
Local $newString = ''
For $i = 0 To UBound($array) - 1 Step + 1
$newString &= $array[$i]
Next
This is the code I use to replace all unnecessary characters. Where "newString" is the new string. In the second parameter of the StringRegExp method you can place new characters that will not be removed.
For the first questions, can you give me some more information about the background of your program?