The widget should support any character you can type, assuming your backend implementation supports it. The only exception is your delimiter character if you've configured it for multi-value mode (where you can enter a list of values, and each one gets independent completion).

I don't really have plans to do much with the widget. I kind of misnamed it. It's not really a combobox, but more an autocompleter. In that regard it's quite functional, and while it's not quite as polished as others (such as the one in Scriptaculous (http://script.aculo.us/), there are a couple edge cases I've run into that it works better for. That has probably changed as others have upgraded, of course. Mine is over two years old.

Adding an explicit trigger (the down arrow) to fire the autocomplete machinery at a time other than when typing triggers it should be pretty trivial. You'll just need to invoke valueChanged on the ComboBox object when the user clicks the arrow. You'll probably need to supply some custom logic in your option-generating callback to handle empty values and generate the top 20 list, but that's a snap. None of the ComboBox code itself should require modification.

http://dev.freightrak.com/CommonFiles/Objects/ComboBox/Test_BasicCombo.asp

I'm also wondering if you have considered placing a arrow to the right for the user to click and select an item from a regular list (e.g. TOP 20 Customers or something loaded upon initializing of the box).

Dave