Find the LENGTH of a string without using LEN Function in Sql Server

CREATE FUNCTION dbo.GetLength(@InputString VARCHAR(8000))
RETURNS INT
AS
/*    -- Comments --
Created By: Alwyn Duraisingh.M
Created on: April 26 2010 10:10 PM 
Purpose: To find the length of the string without using LEN() function
*/
BEGIN
     DECLARE @Count INT, @Index INT, @Flag INT
     SELECT @InputString = REPLACE(@InputString, ' ','*'),
     @Count = 0, @Index = 1, @Flag = 1
     --Looping through each and every character and count one by one
     WHILE ( @Flag = 1 )
     BEGIN
         IF ((SELECT SUBSTRING(@InputString,@Index,1)) <> '')
         BEGIN
              SET @Count = @Count + 1
         END
         ELSE
         BEGIN
              SET @Flag = 0
         END
         SET @Index = @Index + 1
     END
     RETURN @Count
END

SELECT dbo.GetLength('God is only one') AS LENGTH

RESULT:
*******
LENGTH
*******
15