Question : Returning Output parameters from a stored proceedure

I have created a stored proceedure. Now I want to return some values from it. I want to return @resultCode and an inventory list something like this:
itemName Quantity date; itemName Quantity date; itemName Quantity date

I'm getting this error when trying to execute any of my outputs:
Server: Msg 8114, Level 16, State 1, Procedure uspupdatedb, Line 0
Error converting data type nvarchar to int.

Heres my execute:
DECLARE @resultCode int
EXEC Mydb.dbo.uspUpdatedb 2,'scented candle',.5,'7/31/2010',0
Exec @resultCode = uspUpdatedb  OUTPUT

PRINT @resultCode

Here is my stored proceedure:

CREATE PROCEDURE uspUpdatedb

@storeID varchar(100),
@itemName varchar(50),
@Quantity varchar (8),
@date DateTime,
@resultCode int OUTPUT

AS

--SELECT to see if item exists.

IF EXISTS (SELECT * FROM InventoryList a  JOIN StoreList b on a.StoreId=b.StoreId WHERE (a.StoreID=@StoreID) AND (a.ItemName=@ItemName)
AND (a.date=@date ))


--if item found in inventory list
SET @resultCode= 1
PRINT 'This date and quantity are already entered'
END
ELSE
BEGIN
    UPDATE  InventoryList
    SET     Quantity = Quantity + convert(float(8),@Quantity
    WHERE   itemName=@itemName AND StoreID=@StoreID

      SET @resultCode=0

END

--SELECT to see if item doesn’t exist.
IF NOT EXISTS (SELECT * FROM InventoryList a  JOIN StoreList b on a.StoreId=b.StoreId WHERE (a.StoreID=@StoreID) AND (a.ItemName=@ItemName)
AND (a.date=@date ))

--if item not found in inventory list
BEGIN
INSERT INTO InventoryList (StoreID,itemName,Quantity,date) VALUES(@StoreID, @ItemName, convert(float(8),@Quantity, @date)

SET @resultCode=0
END
--returns 0 on successful update or insert  and 1 if error occured
RETURN @resultCode
GO

Thank-you for any help!

Answer : Returning Output parameters from a stored proceedure

DECLARE @resultCode int
SET @ResultCode = 0

EXEC Mydb.dbo.uspUpdatedb @storeID = 2, @itemName = 'scented candle',@Quantity = '.5', @Date = '7/31/2010', @resultCode = @resultCode OUTPUT

PRINT @resultCode