Probelm With Transaction

hi,I wrote this sp :CREATE PROCEDURE ins_AddOrder( @CartId NVARCHAR(50), @CustomerId INT, @OrderDate DATETIME, @OrderId INT OUTPUT)AS

DECLARE @ins_error INT, @sel_error INT, @var_rowcount INT

BEGIN TRAN AddOrder

INSERT INTO tbl_orders( customerId, orderDate)VALUES( @CustomerId, @OrderDate)

-- SET THE @@ERROR VALUE TO @ins_errorSELECT @ins_error =@@ERROR

/*IF INS_ERROR != 0BEGIN ROLLBACK TRAN RETURNEND*/

SELECT  @OrderId = @@identity

INSERT INTO tbl_orderDetails( orderId, productId, quantity, productPrice)SELECT  @OrderId, tbl_product.productId, quantity, tbl_product.productPriceFROM tbl_shoppingCartINNER JOIN tbl_product ON tbl_shoppingCart.productId = tbl_product.productIdWHERE  cartId = @CartId

-- SET THE @@ERROR VALUE TO @sel_errorSELECT @sel_error = @@ERROR

-- SET THE @@ROWCOUNT TO @var_rowcountSELECT @var_rowcount = @@ROWCOUNT

IF  @sel_error <>  0  OR  @var_rowcount = 0 BEGIN  ROLLBACK TRAN AddOrder  RETURN ENDELSE BEGIN  EXEC del_EmptyShoppingCart @CartId  COMMIT TRAN AddOrder ENDGOIn the last few lines i try to prevent adding new row to tbl_orders (first statement), while the SELECT (second statement)  does not return any row .It still not work.Can anyone help please?thanks.