Ending Transactions

Hi Guys,

Im having trouble stopping a transaction once the result on one or more of my sql statements rolls back the transaction. Take a look at one my first 'IF' statement (below).  If the parameter '@Return' is 'False' i want the transaction rolleback and all sql execution to stop. But my problem is the rest of the sql gets executed and i end up getting rubbish data. Im still new to transactions so i think im doing something really wrong. Please take a look at my sql and help me out in what ever way you think is best. thanks in advance.

MattBEGIN TRY

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE

BEGIN TRANSACTION;

BEGIN

DECLARE @Return BIT;

SELECT @Return = (SELECT IsReturnable FROM INVENTORY WHERE InventoryID = 6)

IF (@Return = 'False') ROLLBACK TRANSACTION;

DECLARE @Already_In INT;

SELECT @Already_In = (SELECT ReturnedBy FROM InventoryInUse WHERE (CheckOutNumber = 375))

IF (@Already_In IS NOT NULL) ROLLBACK TRANSACTION;

DECLARE @Outstanding As INT;

SELECT @Outstanding = (SELECT (QtyTaken - 40) AS Outstanding FROM InventoryInUse WHERE (CheckOutNumber = 375));

DECLARE @OutstandingReason As VARCHAR(200);

DECLARE @Get_Person_ID INT;

Select @Get_Person_ID = (SELECT PersonID From [User] WHERE Username = 'matthewsk');

IF (@Outstanding < 0) ROLLBACK TRANSACTION;

ELSE IF (@Outstanding > 0)BEGIN

IF (@OutstandingReason = '') SELECT @RollBack = @RollBack + 1;

UPDATE InventoryInUse SET ReturnedBy = @Get_Person_ID, ReturnDate = GETDATE(), QtyReturned = 40, QtyOutstanding = @Outstanding, WriteOffReason = 'Testing This' WHERE (CheckOutNumber = 375);

UPDATE Inventory SET TotalQty = TotalQty - @Outstanding, QuantityInUse = QuantityInUse - (40 + @Outstanding) WHERE InventoryID = 6;

END;ELSE IF (@Outstanding = 0)

BEGIN

UPDATE InventoryInUse SET ReturnedBy = @Get_Person_ID, ReturnDate = GETDATE(), QtyReturned = 50 WHERE CheckOutNumber = 375;

UPDATE Inventory SET QuantityInUse = QuantityInUse - 50 WHERE InventoryID = 6;

END;

COMMIT TRANSACTION;

END;END TRY

BEGIN CATCH IF (XACT_STATE()) = -1

BEGIN ROLLBACK TRANSACTION;

 

END;

END CATCH;