The tabs can be refreshed (and hence displayed, or hidden) anytime a field completes.
Let's say you have a checkbox field, called Daisy. Is Daisy is true then CustomerTab appears, if it is false then CustomerTab disappears.
The works in 2 parts;
a) The Hide condition for the Customertab is set to something like
p_web.GSV('daisy') = true
b) On the Daisy field, on the client side tab, add CustomerTab to the Reset List.
So the checkbox "resets" the tab, and the tab is dependent on the value in Daisy.
cheers
Bruce