i presume you have changed the Listbox so that its selectionMode property is set to multiple (either Multisimple or MultiExtended)

vb Code:
  1. Private Sub multiButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _
  2.     Handles multiButton.Click
  3.  
  4.         Me.resultLabel.Text = String.Empty
  5.  
  6.         If Me.namesListBox.SelectedItems.Count > 0 Then
  7.             For Each itm As String In Me.namesListBox.SelectedItems
  8.                 Me.resultLabel.Text &= itm & Environment.NewLine
  9.             Next
  10.         End If
  11.  
  12. End Sub