--Pre-populate with characters of length > 1
DECLARE @Lengths TABLE(Ch CHAR(1) PRIMARY KEY, Length INT)
INSERT INTO @Lengths(Ch,Length)
SELECT 'A',2 UNION ALL
SELECT 'E',2

Declare @Text1 Varchar(max)
Set @Text1 ='Test Message'


SELECT SUM(COALESCE(l.Length,1))
FROM Numbers n
LEFT OUTER JOIN @Lengths l ON l.Ch=SUBSTRING(@Text1,n.Number,1)
WHERE n.Number BETWEEN 1 AND LEN(@Text1)