Fill Check in Form With Input Restrictions

Hello everybody!
I’ve just started studying 1C thus I’m asking to help solving the simple problem:
There is a form with City, Area and Address fields. It is required to make Area inactive while the City is empty and make Address inactive while Area is empty. How to make a condition to force the user to input City prior Area and Area prior Address?

Hi!
For an example,

&AtClient
Procedure ManagementOfVisibility()
if ValueIsFilled(City) then
Items.Area.Enabled = true;
else
Items.Area.Enabled = false;
endif;
if ValueIsFilled(Area) then
Items.Address.Enabled = true;
else
Items.Address.Enabled = false;
endif;
EndProcedure

This example is valid for the managed forms.
Names of requisites and form fields are coincide.

Thank you, Victor!
That worked for me!