Parcheesi Blockade Rule
Proposed answer : A new blockade cannot be formed

Parcheesi is the trademarked name of the American version of the Indian game Pachisi.
Milton-Bradley and Parker Brothers sold the game under this name and were acquired by Hasbro.

The Parker Brothers rules do not address the problem presented here.
Parker Brothers Parcheesi Rules

The Milton-Bradley rules do explicitly address the situation.

Milton-Bradley Parcheesi rules



Answer. You are not allowed to form a new blockade from an existing blockade.