That's because the combobox is not a true combobox. It is an activeX control and connects to a manager control. The manager control talks to it and tells it what should be selected. Or the manager control listens to it and when the user changes the selection then the manager control pushes that out to all other connected controls.
In order to get the path you need to use the SequenceFileView manager that the combobox is connected to.
SequenceFileViewMgr.SequenceFile.Path
Hope this helps,