Using RAISERROR isn't working in SQL Server 2005?

Error is occurring because you directly using function in Raiserror(notice single e) so to avoid this try the below code Try this is working for me

BEGIN CATCH
    DECLARE @ErrorMessage NVARCHAR(4000);
    DECLARE @ErrorSeverity INT;
    DECLARE @ErrorState INT;

    SELECT 
        @ErrorMessage = ERROR_MESSAGE(),
        @ErrorSeverity = ERROR_SEVERITY(),
        @ErrorState = ERROR_STATE();

    RAISERROR (@ErrorMessage, -- Message text.
               @ErrorSeverity, -- Severity.
               @ErrorState -- State.
               );
END CATCH;

RAISERROR follows the same rules as any other stored procedure call. Parameters passed in must be a constant or a variable. You cannot pass a function directly as a parameter. See Executing Stored Procedures for documentation on this.

/* Demo Code - Functions accept functions as parameters
               while stored procedures do not              */

create function dbo.fnDayOfWeek 
    (@date datetime) 
    returns int
as
begin
    declare @x int
    set @x = DATEPART(day,@date)
    return (@x)
end
go

/* Both statements are successful */
select dbo.fnDayOfWeek('2010-08-06')
go
select dbo.fnDayOfWeek(GETDATE())
go

drop function dbo.fnDayOfWeek
go

create procedure DayOfWeek
    @date datetime
as
begin
    select DATEPART(day,@date)
end
go

/* First call succeeds, second fails */
exec DayOfWeek @date = '2010-08-06'
go
exec DayOfWeek @date = getdate()
go

drop procedure DayOfWeek
go