Adding Search Providers From Webpages?

I've been working on some autocomplete abilities for a webbrowser I'm building, rather like in IE or Firefox. This is what I mean: I have absolutely everything working - adding search providers from webpages, getting the search suggestions as an XML file from whatever provider may be being used, and adding them in a multithreaded manner to the combobox with all the suggestions in it.

But there's a problem. Due to the fact that the search suggestions are only retrieved (in a matter of milliseconds) after the user has typed something in the Combobox, the suggestions only flicker up, as they are modified just after the text is changed, therefore I get an effect like this:

Again, I'm pretty sure I'm getting this effect because of the fact that I'm adding the Auto Complete suggestions to the combobox right after the text is changed - so they just hide themselves again - and this process is repeated. Does anyone know any way in which I might be able to stop this disappearing from happening? Because I've had a good think about it and I can't really think of any workarounds.