Pass Url To A Popup

In my program the user clicks on a link and using the window.open
function, opens a new window.

I pass a url to the new window like this:

<a href="#"
onClick="window.open('../quotescreenwindow.php?enroll_id=enrollwindowprime. php',
'WindowC', 'width=750,height=800,scrollbars=yes');">

In the new window that just opened called quotescreenwindow.php, I
have a button that when clicked, should open yet another window called
enrollwindowprime.php (this is the variable I am passing after the
question mark).

What I cannot do, is to grab this variable that I am passing to the
first window I open and use its content to open the next window.

I am not very experienced and have been piecing this together from
various web sites.

To simplify all of this:

Screen A Opens Popup Window B and passes it a variable with a url
inside of it.

Popup Window B wants to use the variable with the url to open Pop Up
Window C.