/*Delimiter variables, first and second position*/
DECLARE @dfp AS CHAR(1);
DECLARE @dsp AS CHAR(1);
DECLARE @text VARCHAR(MAX);
SET @dfp = ';';
SET @dsp = '@';
SET @text = 'I want you to ;Extract this@ substring for me please.';
SELECT SUBSTRING(@text, (CHARINDEX(@dfp, @text) + 1), (CHARINDEX(@dsp, @text) - 2) - CHARINDEX(@dfp, @text) + Len(@dsp))