.NET CF ComboBox没有DropDown事件，那么替代方案是什么？

I'm working on a .NET 3.5 SmartDevice project and I could really use the ComboBox DropDown event, but the .NET Compact Framework version doesn't have it. Is there another way to be made aware of when the list has dropped down?I'm working on a .NET 3.5 SmartDevice project a