All that is needed to create a UCC/EAN128 barcode is to append a FNC 1 (ASCI 185) to the begining of the value. Below is a very brief Visual Basic .net example.
Private Sub cmdSubmit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSubmit.Click
Dim sFnc1 As String
' UCC 128 is simply a Code 128 with a (Function 1) FNC 1 character at the beginning
' of the value.
sFnc1 = Chr(185) ' set up the FNC 1 character.
' The Drawing control's symbology was set to Code 128 at design time, so all we need to
' do here is append the Function 1 to the beginning of the value.
bcMain.Value = sFnc1 & txtValue.Text ' This code pulls its value from a text box.