If you want to include incremental search functionality to the BrowseDialog, you'll most likely have to do so by using the soure code file for the BrowseDialog and modifying it... there's not really any way to extend it and provide that functionality. The reason being is that each type you type a character, you need to query the database for the proper data... and you'll end up with the functionality similar to an "auto-complete" textbox where as you type, it searches for possible options to complete for you. You would also need to make these database queries asynchronous since you cannot pause the UI in between each keypress to retrieve the next set of records. And when you get into asynchronous processing, you'll need to make sure you synchronize your thread through an ISynchronizeInvoke object on the main thread (usually the BrowseDialogForm itself). Those topics are way more advanced than I have time to get into on the forum, but MSDN's documentation has lots of info on it if you search for "async calls" and "ISynchronizeInvoke".
Have fun with that