public static function columnIndexFromString($pString = 'A')
	{
		//	Using a lookup cache adds a slight memory overhead, but boosts speed
		//	caching using a static within the method is faster than a class static,
		//		though it's additional memory overhead
		static $_indexCache = array();

		if (isset($_indexCache[$pString]))
			return $_indexCache[$pString];

		//	It's surprising how costly the strtoupper() and ord() calls actually are, so we use a lookup array rather than use ord()
		//		and make it case insensitive to get rid of the strtoupper() as well. Because it's a static, there's no significant
		//		memory overhead either
		static $_columnLookup = array(
			'A' => 1, 'B' => 2, 'C' => 3, 'D' => 4, 'E' => 5, 'F' => 6, 'G' => 7, 'H' => 8, 'I' => 9, 'J' => 10, 'K' => 11, 'L' => 12, 'M' => 13,
			'N' => 14, 'O' => 15, 'P' => 16, 'Q' => 17, 'R' => 18, 'S' => 19, 'T' => 20, 'U' => 21, 'V' => 22, 'W' => 23, 'X' => 24, 'Y' => 25, 'Z' => 26,
			'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5, 'f' => 6, 'g' => 7, 'h' => 8, 'i' => 9, 'j' => 10, 'k' => 11, 'l' => 12, 'm' => 13,
			'n' => 14, 'o' => 15, 'p' => 16, 'q' => 17, 'r' => 18, 's' => 19, 't' => 20, 'u' => 21, 'v' => 22, 'w' => 23, 'x' => 24, 'y' => 25, 'z' => 26
		);

		//	We also use the language construct isset() rather than the more costly strlen() function to match the length of $pString
		//		for improved performance
		if (isset($pString{0})) {
			if (!isset($pString{1})) {
				$_indexCache[$pString] = $_columnLookup[$pString];
				return $_indexCache[$pString];
			} elseif(!isset($pString{2})) {
				$_indexCache[$pString] = $_columnLookup[$pString{0}] * 26 + $_columnLookup[$pString{1}];
				return $_indexCache[$pString];
			} elseif(!isset($pString{3})) {
				$_indexCache[$pString] = $_columnLookup[$pString{0}] * 676 + $_columnLookup[$pString{1}] * 26 + $_columnLookup[$pString{2}];
				return $_indexCache[$pString];
			}
		}
		throw new PHPExcel_Exception("Column string index can not be " . ((isset($pString{0})) ? "longer than 3 characters" : "empty"));
	}