Transacciones a través de Instrucciones Sql

[michugg]

Hola
Estoy utilizando un adocommand para poder actualizar una tablas de la base de datos tengo este codigo
ADOCInventoryUser.Parameters.FindParam('IdPODetail').Value :=
ClientDataSetDetailIdPODetail.Value;
ADOCInventoryUser.Parameters.FindParam('SoldBoxes').Value :=
ClientDataSetDetailSoldBoxes.Value;
ADOCInventoryUser.Execute;
Y en la propiedad commandtext tengo
DECLARE @SoldBoxes INT
SET @SoldBoxes := SoldBoxes
DECLARE @IdPODetail INT
SET @IdPODetail := IdPODetail
DECLARE @IdUser INT
SET @IdUser :=IdUser
DECLARE @IdCustomer INT
SET @IdCustomer :=IdCustomer
UPDATE tblInventory
SET StockBoxes=StockBoxes - @SoldBoxes
WHERE IdPODetail = @IdPODetail
UPDATE tblInventoryUser
SET SoldBoxes=SoldBoxes + @SoldBoxes
WHERE IdPODetail = @IdPODetail
AND IdUser = @IdUser
AND IdCustomer =@IdCustomer
INSERT INTO tblInventoryUser(IdPODetail,IdUser,SoldBoxes,IdCustomer)
SELECT @IdPODetail, @IdUser, @SoldBoxes, @IdCustomer
WHERE @IdPODetail NOT IN (
SELECT IdPODetail
FROM tblInventoryUser
WHERE IdPODetail=@IdPODetail AND IdUser=@IdUser AND IdCustomer =@IdCustomer)

Pero me da el siguiente error Access violaton at address004FEDC9 in module Flw.exe read of address 000000C
Porfavor necesito ayuda
Gracias