Have a list box with item names in it with an array to assign price. when selected a text box displays the price. What I want is when the user clicks the "Add Item to Shopping Cart" button, the item name is stored in another list box while the price is multiplied by the number and sent to a subtotal label. The user should be able to add multiple items to the Shopping Cart list box before purchasing. Here's what I have now:

Private Sub btnAddItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAddItem.Click
Dim lboxItemName As ListBox
Dim lboxItemsPurchased As String
Dim txtboxItemsPurchase As String
Dim Subtotal As Decimal
Dim TaxAmt As Decimal
Dim Total As Decimal
Dim itemprice As Decimal
Dim itemquantity As Decimal

'Convert text boxes to Decimals
itemprice = CDec(txtboxItemPrice.Text).ToString("C")
itemquantity = CDec(txtboxItemQuantity.Text).ToString("C")

'Move selected items into shopping cart and Calculate subtotal
'lboxItemsPurchased.Text = lboxItemName.Items(lboxItemName.SelectedIndex)
Subtotal += itemprice * itemquantity

'Display in subtotal
lblSubTotal.Text = Subtotal.ToString("C")

End Sub