Dim NowIndex As Integer = -1
Private Sub ComboBox1_SelectionChangeCommitted(ByVal sender As Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectionChangeCommitted
If Not NowIndex.Equals(Me.ComboBox1.SelectedIndex) Then
If MsgBox("真的更改吗?", MsgBoxStyle.OKCancel, "注意") = MsgBoxResult.OK Then
'处理
NowIndex = Me.ComboBox1.SelectedIndex
Else
'不处理
Me.ComboBox1.SelectedIndex = NowIndex
End If
End If
End Sub