Use the listindex property
If you add the product code and product seperately to two list boxes in one loop you can use the listindex of both combo boxes is the same.
To be sure you also use the Itemdata property of both combo boxes to store the new listindex value of the other combobox which item was added.
Code:
cmbProduct.Additem rs!Name
cmbCode.Additem rs!Code
cmbProduct.Itemdata(cmbProduct.NewIndex) = cmbCode.NewIndex
cmbCode.Itemdata(cmbCode.NewIndex) = cmbProduct.NewIndex
Same goes for listindex controls
You could also consider adding a autonumber field to the table, this always creates a unique long number ID for the record to reference to. You can still use the Code field as your Primary Index.
Hope this helps