Text: immutable strings

Hi all,

I have a Text() widget and I want to display some values tab formatted.
The values should be prefixed  with a text-label which is immutable by the user
something like

  label: value            label: value

the user should be able to edit the values but not the labels.
I know that I can insert the label as a window create_window(Label())
but for very big files it becomes extremely slow

If I tag the labels, can I forbid the Text widget to disallow the text editing
over this specific tag?

Thanks in advance
Vasilis