在DataGridView中获取ComboBox的DropDown事件的最佳方法是什么

Say I have a DataGridView in which I dynamically build up a ComboBox column and add values to it. What's the best approach to trapping when the user clicks on the drop down button to show the drop down list. If I simply use CellClick on the DataGridView, I get that event even if the user doesn't actually click on the drop down button.Say I have a DataGridView in which I dynamicall