Here is a quick method. NOT recommended for speed or flexibility ... If you would outline your requirements in greater detail perhaps some one can / will give you further assistance.

CREATE TABLE For_Test(ID int not null,Name varchar(255),Amount decimal(18,2))

INSERT INTO For_Test VALUES (1,'A',220),(2,'B',340),(3,'C',540)

,(4,'D',780)

--I just want to add amount of ID 1,2 and 3 excluding 4.

SELECT SUM(Amount) FROM For_Test WHERE ID in (1,2,3)

--Different select statement but same result

SELECT SUM(Amount) FROM For_Test WHERE ID <> 4

--Yet a 3rd way

SELECT SUM(Amount) FROM For_Test WHERE ID < 4

--Yet a 4th way - using MOD function

SELECT SUM(Amount) FROM For_Test WHERE ID % 4 <> 0;

Result:

(No column name)

1100.00