More context, please. Is $ws a worksheet? If so, I'm wondering how this works -- I don't see a TextBoxes object in the Worksheet or Worksheets object (in the Object Browser).
If you can get a handle to a Range object, though, there is an Unmerge function available to break up grouped cells. You can see this yourself by looking at the Object Browser -- press Alt-F11 in Excel to bring up the VB editor, then F2 to get the Object Browser. Then I usually restrict the search to Excel only (change where it says "all libraries" to "Excel").
Edit to add: Note that it's very possible that the TextBoxes item is just not part of the version of Excel I have available to me at work (Excel 2000).