Insert into a table excluding duplicates of a selected column

Question

I have mytable:
IDNO
Item
Date
Level
1
X24
12/23/13 10:41
22996
2
X24
12/23/13 10:41
22996
3
X24
12/23/13 9:21
23256
4
X24
12/23/13 9:21
23256
5
X24
12/23/13 9:22
23256
6
X24
12/23/13 9:22
23256
7
X24
12/23/13 9:22
22916
that is a result of INSERT i.e.,
INSERT INTO myTABLE(Item,[Date],[Level])
values('X24','12/23/13 :22','22916')
I want the INSERT to exclude the duplicate level defined as the previous level in a selected column [Level]. This would avoid having to 'view' the table using:
SELECT
i.IDNO,i.[Date],i.[Level]
FROM
mytable
i
INNER
JOIN
mytable
d
ON
d.IDNO
=
i.IDNO-1
WHERE
i.[Level]
<>
d.[Level]
IDNO is an identity column.
How can this INSERT be achieved without the overheads? 

Answer 1

Quite helpful comments particularly the ISO- 11179 and the design elements that can prevent the problem in the first instance. My apologies with regards to my impolite post omitting the DDL.  It is a small procedure and [Date] and [Level] can be accommodated
by the server but are bad habits. My efforts to control the data input were in vain as the data was not from a software conducive to such controls. Because of the high frequency volume of the data, (suggested by the time-stamps with milliseconds cut), any
effort to have 'The data... cleaned in a presentation/input layer ' would be futile.  The suggestions of  yourself
and Erland Sommarskog, SQL Server MVP, [email protected], of a UNIQUE constraint to deal with the problem
underscores the importance of design even in the 'smallest' of procedures. 
This worked:
drop table Foobar
CREATE TABLE Foobar
(item_name CHAR(5) NOT NULL, 
 foo_timestamp DATETIME2(0) NOT NULL
  CHECK (foo_timestamp 
    = DATEADD(MINUTE, DATEDIFF(MINUTE, '2000-01-01', foo_timestamp),
     '2000-01-01')),
 water_level INTEGER NOT NULL, -- why not be silly? 
 PRIMARY KEY (item_name,foo_timestamp, water_level));
INSERT INTO Foobar
VALUES
('X24', '2013-12-23 10:41:00', 22996), 
-- ('X24', '2013-12-23 10:41:00', 22996), rejected by DDL!!
-- ('X24', '2013-12-23 09:21:00', 23256), rejected by DDL!!
('X24', '2013-12-23 09:21:00', 23256), 
('X24', '2013-12-23 09:22:00', 23256), 
-- ('X24', '2013-12-23 09:22:00', 23256), rejected by DDL!!
('X24', '2013-12-23 09:22:00', 22916);
select *
from Foobar
item_name foo_timestamp
water_level
X24   2013-12-23 09:21:00
23256
X24   2013-12-23 09:22:00
22916
X24   2013-12-23 09:22:00
23256
X24   2013-12-23 10:41:00
22996