How to send the variable between 2 page ?

sorry, I don't know how to explain me question.
Let me show by this example.

Process :
1, a(A.html) send a variable to b(b.html). --> This is easy.
(b is open by a, so a is parent. And the b is top up)

2, when i finish the job in b. I will submit that. --> OK
(when submit(), the window will close)

3, Now the problem, how can i send back the info to parent(a or a.html) ???
(Some think like auto refresh the a by b)

Thank you

I hope have a complete's source code.

you may send the information to page a before starting submisition from page b, by inserting a return conditioner.

something like:

<form onsubmit="return function(){parent.object.value=this.elements['elementname'].value}">