_LevenshteinDistance

[WarMan]

About Levenshtein distance

Func _LevenshteinDistance($s1, $s2)
    Local $len1 = StringLen($s1), $len2 = StringLen($s2)
    If $len1 = 0 Then Return $len2
    If $len2 = 0 Then Return $len1

    Local $v0[$len2 + 1], $v1[$len2 + 1]
    For $i = 0 To $len2
        $v0[$i] = $i
    Next

    For $i = 0 To $len1 - 1
        $v1[0] = $i + 1
        For $j = 0 To $len2 - 1
            Local $cost = (StringMid($s1, $i + 1, 1) = StringMid($s2, $j + 1, 1)) ? 0 : 1
            $v1[$j + 1] = ($v0[$j + 1] + 1 > $v1[$j] + 1 ? $v1[$j] + 1 : $v0[$j + 1] + 1) > $v0[$j] + $cost ? $v0[$j] + $cost : ($v0[$j + 1] + 1 > $v1[$j] + 1 ? $v1[$j] + 1 : $v0[$j + 1] + 1)
        Next
        Local $temp = $v0
        $v0 = $v1
        $v1 = $temp
    Next

    Return $v0[$len2]
EndFunc

[AspirinJunkie]

The following UDF may also be of interest to you, as it expands on the idea of the Levenshtein distance:
>>Fuzzy String UDF<<