Incorrect Value Returned From Stored Procedure

I have an asp.net 1.1 website that uses sql server 2000 and vb.
I have a bit of a dilema, when I run a stored procedure in a webpage it returns the wrong value, but if I run it
in the query analyzer the correct value is returned. Dim orderHistory As nlb.OrdersDB = New nlb.OrdersDB

' Obtain Order ID from QueryString
Dim OrderID As Integer = CInt(Request.Params("ID"))

' Get the customer ID too
Dim myNewCustomerId As Integer = 0
myNewCustomerId = orderHistory.GetOrderCustomer(OrderID)



Public Function GetOrderCustomer(ByVal orderID As Integer) As Integer

' Create Instance of Connection and Command Object
Dim myConnection As SqlConnection = New SqlConnection(ConfigurationSettings.AppSettings("ConnectionString"))
Dim myCommand As SqlCommand = New SqlCommand("nlbsp_OrdersCustomerID", myConnection)

' Mark the Command as a SPROC
myCommand.CommandType = CommandType.StoredProcedure

' Add Parameters to SPROC
Dim parameterOrderID As New SqlParameter("@order_id", SqlDbType.Int, 4)
parameterOrderID.Value = orderID
myCommand.Parameters.Add(parameterOrderID)

Dim parameterOrderCustID As New SqlParameter("@customer_id", SqlDbType.Int, 4)
parameterOrderCustID.Value = ParameterDirection.Output
myCommand.Parameters.Add(parameterOrderCustID)

'Open the connection and execute the Command
myConnection.Open()
myCommand.ExecuteNonQuery()
myConnection.Close()

' Return the customer_id (obtained as out paramter of SPROC)

If parameterOrderCustID.Value <> 0 Then
Return CInt(parameterOrderCustID.Value)
Else
Return 0
End If

End Function


the stored procdure is
CREATE PROCEDURE [dbo].[nlbsp_OrdersCustomerID]
(
@order_id int,
@customer_id int OUTPUT
)
AS

/* Return the customer_id from the Orders. */
SELECT
@customer_id = customer_id

FROM
nlb_Orders

WHERE
order_id = @order_id
GO


 I know a particular order_id returns a value of 1. But when I run it in the webpage it always comes back as 2.
 
Any ideas would be appreciated
 
Thanks
Pete