Hi Kate
When your Spy++ tells you that its a ThunderRT6ListBox, you can't be sure that the control has implemented a provider for UIAutomation or MSAA. I've lately been doing a lot of work automating VB6 applications with white and build providers for UIAutomation, and my experience is that there is only a few of these advanced VB6 control that supports automation.
To a start you should try figure out which classname the using autoit, you might find that the ThunderRT6ListBox has a different classname. But if white hasn't any direct support for the control, then you need to develop a UIAutomation Provider to support it. That's a steep learning curve but doable :)
But start with posting the real classname for the control or if possible ask the developers of the vb6 application which control they have used and from which library they have taking it from.
Best regards
Jakob Øjvind Nielsen
Testware ApS