How Should I Write This Query Wiht Case Statements

Hi

  I have a stored procedure and i am trying to add case statements to them.. but i am getting an Error. which is

Msg 125, Level 15, State 3, Procedure udf_EndDate, Line 34

Case expressions may only be nested to level 10.

 

And This is my sproc-- ================================================
-- Template generated from Template Explorer using:
-- Create Scalar Function (New Menu).SQL
--
-- Use the Specify Values for Template Parameters
-- command (Ctrl-Shift-M) to fill in the parameter
-- values below.
--
-- This block of comments will not be included in
-- the definition of the function.
-- ================================================
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:<Author,,Name>
-- Create date: <Create Date, ,>
-- Description:<Description, ,>
-- =============================================
Create FUNCTION [dbo].[udf_EndDate] (@PeriodId int)
RETURNS datetime
AS

BEGIN
DECLARE
@Month int,
@Year char(4)

SELECT
@Month = [Month],
@Year = Cast([Year] as char(4))
FROM
Period
WHERE
PeriodId = @PeriodId

RETURN
CASE @Month WHEN 1 THEN '1/31/' + @Year ELSE
CASE @Month WHEN 2 THEN '2/28/' + @Year ELSE
CASE @Month WHEN 3 THEN '3/31/' + @Year ELSE
CASE @Month WHEN 4 THEN '4/30/' + @Year ELSE
CASE @Month When 5 Then '5/31/' + @Year ELSE
CASE @Month When 6 Then '6/30/' + @Year ELSE
CASE @Month When 7 Then '7/31/' + @Year ELSE
CASE @Month When 8 Then '8/31/' + @Year ELSE
CASE @Month When 9 Then '9/30/' + @Year ELSE
CASE @Month When 10 Then '10/31/' + @Year ELSE
CASE @Month When 11 Then '11/30/' + @Year ELSE
CASE @Month When 12 Then '12/31/' + @Year ELSE null END
END
END
END
END
END
END
END
END
END
END
END
END


Any help will be appreciated.

 

Regards

Karen