No additional code  needed.

From the VB Editor, set the Visible Properties on the data  worksheet
to Very Hidden. Your Form can still write to a hidden worksheet. In
the VBE, look at the VBAProject Properties for your project
(Right-Click on your project) and Lock the project  for viewing.

Anyone savvy enough - and mean enough - can still overwrite your data
but it'll make it much more difficult to do so. Most Users that I
work with don't even know that there is a VB Editor.