How to Get sum of first record amount and second amount is in Total Amount using Sql server STored Procedure

 USE [temp]
GO
/****** Object:  Table [dbo].[TblTest]     ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[TblTest](
	[temp_id] [int] IDENTITY(1,1) NOT NULL,
	[temp_name] [varchar](50) NULL,
	[sum] [int] NULL,
	[Total_sum] [int] NULL
) ON [PRIMARY]

GO
SET ANSI_PADDING OFF

Alter procedure ProcTestGet
@temp_name varchar(50),
@sum int
AS
 Declare @Tmp_id As int
 Declare @total_sum As int 
Declare @sum1 As int
select @Tmp_id = @@identity
If @Tmp_id = 0          
Begin        
		set @total_sum =Null  
		insert into TblTest(temp_name,sum,total_sum) VALUES(@temp_name,@sum,@total_sum)
End        
else
begin
		select @total_sum = total_sum  from TblTest where temp_id = @@identity
		if @total_sum  = NULL
		begin
			select @sum1= sum from TblTest where temp_id = @@identity
			declare @totalsum int
			set @totalsum =  @sum1 + @sum
			insert into TblTest(temp_name,sum,total_sum) VALUES(@temp_name,@sum,@totalsum)
		end
		else
		begin
			select @total_sum = total_sum  from TblTest where temp_id = @@identity
			declare @totalsum1 int
			set @totalsum1 = @total_sum + @sum
			insert into TblTest(temp_name,sum,total_sum) VALUES(@temp_name,@sum,@totalsum1)
		end
select @@identity
End