Visual Basic: Making multiple forms for an order - vb.net

Question

I've been working on this project for two weeks now and I'm drained from all the hiccups I've come across. Now I've hit a brick wall.
I'm making a "simple" order form in Visual Basic 2010 that calculates the amount due for an order and then from the total determines what the shipping will be. I've been able to accomplish the following tasks:
accept customer data (name, address, city, state abbreviation, zipcode)
calculate total with shipping costs (accurately, for the most part)
clear the order form and exit
But the way I have it right now, a customer can only put in 1 order form.
Problem: I have to figure out a way to allow a customer to place an order form for multiple items. (I'll assume that a customer will not place an order for more than 20 items). So what would be the best way to go about saving the information for multiple items then calculating the cost at the end?
If it's multiple form creation, how is that done? Is the keyword "Container" the way to go, and how? At the end of the day, I just don't know how to create this multiple item form (it's like a database in Visual Basic), so any method, at least pointing me in the right direction, would be helpful.
(Tried to post an image of my work so far but I'm new here - can't post images yet. I've posted a bit of my code below - code works for 1 order)
Snippet Code:
Private Sub total_mouseleave(ByVal sender As Object, ByVal e As EventArgs) Handles total.MouseLeave
Dim gs_1 As Decimal = 4.95
Dim gs_2 As Decimal = 6.95
Dim gs_3 As Decimal = 8.95
Dim gs_4 As Decimal = 10.95
Dim gs_5 As Decimal = 12.95
Dim ex_1 As Decimal = 14.95
Dim ex_2 As Decimal = 16.95
Dim ex_3 As Decimal = 18.95
Dim ex_4 As Decimal = 20.95
Dim ex_5 As Decimal = 22.95
Dim totalcost As Decimal
totalcost = Convert.ToDecimal(total.Text)
If gs_radiobutton.Checked Then
If (totalcost < 1) Then
total.Text = Val(0)
shipping.Text = Val(0)
ElseIf (1 < totalcost AndAlso totalcost < 15) Then
total.Text = Val(totalcost + gs_1)
shipping.Text = ground_1
ElseIf (15 < totalcost AndAlso totalcost <= 49.99) Then
total.Text = totalcost + gs_2
shipping.Text = gs_2
ElseIf (50 < totalcost AndAlso totalcost <= 99.99) Then
total.Text = totalcost + g_3
shipping.Text = gs_3
ElseIf (100 < totalcost AndAlso totalcost <= 199.99) Then
total.Text = totalcost + gs_4
shipping.Text = gs_4
Else
total.Text = totalcost + gs_5
shipping.Text = gs_5
End If
End If
'// . . . .
End Sub

Answer 1

It's not clear from your post if you mean order forms as in a Form object within VB or an order placed by the user.
If you meant orders placed by the user then it would be simpler to use a single form but create a few custom classes to hold all the order line details:
' Class used for each order line
Public Class orderline
Public Value As Decimal
Public StockID As Integer
Public Qty As Integer
End Class
' Class used to store the entire order
Public Class Order
' List of orderlines (similar to an array)
Public OrderLines As List(Of orderline)
Private _totalcost As Decimal
Public ReadOnly Property TotalCost As Decimal
Get
Dim t As Decimal
For Each l In OrderLines
t = t + (l.Value * l.Qty)
Next
Return t
End Get
End Property
End Class
Then in the form you can use the classes as below:
Public Class Form1
Dim ord1 As New Order
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
TextBox1.Text = ord1.TotalCost
End Sub
End Class
You can then create more than one order stored on the form using a list:
Dim CustomerOrders as List<Of Order>

Answer 2

You should be able to create multiple instances of a form and show them non-morally. Whether this is the best design is another discussion.
The non-modal forms would all be visible and can be 'owned' by a main form.
Try something like this:
Dim firstInstance As New YourForm()
Dim secondInstance As New YourForm()
firstInstance.Show() 'Not ShowDialog()
secondInstance.Show(myParent) 'Optional parent form parameter
You'll need to watch the scope of your form instances as the forms will be closed if the variables go out of scope.
This may not be the ultimate solution, but it's something you can try on the way to finding the optimal approach.
Considering the latest comment:
The problem is not clear. Do you want to create multiple forms, one form per order? Or do you want one form that can show multiple orders?
My solution will allow you to show multiple forms while the other answer posted suggests a neat solution to creating one form with multiple orders.
Personally, I would create a single form that shows multiple orders, ListView maybe, that provides some way of viewing/editing each order's details and then allowing the orders to be submitted in a batch. It's more complex but would be more usable, IMHO.