To Add Items to the Shopping Cart, simply create a Hyper Link to the Shopping Cart passing ItemNo and Qty (if needed).
For example, to send Item # 100023 to the Shopping Cart with a Qty of 1, Create a Hyper Link like the following:
CartForm.aspx?ItemNo=100023
To send Item # 100023 with a Qty of 3, do the following:
CartForm.aspx?ItemNo=100023&Qty=3