Show error when same record exists in SQL Server Database

ALTER procedure [dbo].[insertestate1]
	 @position nvarchar(max)
	,@Transfer nvarchar(20)
	,@Type nvarchar(20)
	,@Behcode nvarchar(10)
	,@Measure varchar(20)
	,@code varchar(20)
	,@id int =0
	,@Success VARCHAR(10) OUTPUT
AS BEGIN
IF NOT EXISTS(SELECT behcode FROM Estate_p WHERE code = @code)
    BEGIN
    INSERT INTO Estate_p
	(
		 position
		,[Type]
		,Transfer
		,Code
		,behcode
	)
	VALUES
	(
		 @position
		,@Type
		,@Transfer
		,@code
		,@Behcode
	)
	SET @Success = 'TRUE'
    END
ELSE
	SET @Success = 'FALSE'
END