It was recommended in a prior thread to use FollowHyperlink method on your textbox value. Seems like you didn't follow that advice so you're still struggling. At this point, why not have 1 command button to navigate to a folder and 1 to pick a file, storing each in their own respective textboxes. You could hide the folder path textbox and give user the option of navigating to the folder or file using either button.
Or you can stick with what you have and show the full path in a single textbox. To open to the folder level, in code you'd trim everything off after the last \ using a combination of Right and Len functions. That would give you the folder path. For this, you'd need some way to differentiate which one you want to follow - folder or file path when you FollowHyperlink.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.