I am not sure you can put a field on the layout tab, but you can easily modify the tab name with a reactor based on the value a field might have.
Lets presume that you want the field to be the area of a hatch ... there are several ways to accomplish this
Set a reactor to fire whenever the drawing is issued a regen
Your reactor will find the hatch in question, return the area, formulate the string and update the layout tab
Of course identifying the hatch might be an issue, so the next alternative might be to set a dictionary value in the drawing that contains the handle of the hatch. It will make identification of the hatch simple, but not foolproof.
I think it could be done, but there would have to be some serious error checking