Would this be the code to use?

USE master;

GO

CREATE LOGIN login_test WITH PASSWORD = '3KHJ6dhx(0xVYsdf' MUST_CHANGE,

CHECK_EXPIRATION = ON;

GO

GRANT VIEW SERVER STATE TO login_test;

GO

CREATE TRIGGER connection_limit_trigger

ON ALL SERVER WITH EXECUTE AS 'login_test'

FOR LOGON

AS

BEGIN

IF ORIGINAL_LOGIN()= 'login_test' AND

(SELECT COUNT(*) FROM sys.dm_exec_sessions

WHERE is_user_process = 1 AND

original_login_name = 'login_test') > 3

ROLLBACK;

END;