Launch a pop up window with another larger background window?

How do you launch a small and centered popup window at the same time that you open another html window as background?
I tried to do this but it doesn’t always work. Especially if you return to the opening and begin again, the small centered window doesn’t appear. I used the code from Kirupa to launch the centred popup window and I added my own bit -getURL(“white.html”, “_parent”); here it is complete code:

on (release) {
getURL(“white.html”, “_parent”);
// customize the window that gets opened
// 0 equals NO.
// 1 equals YES.
address = “museum.html”;
target_winName = “introduction”;
width = 700;
height = 600;
toolbar = 0;
location = 0;
directories = 0;
status = 0;
menubar = 0;
scrollbars = 0;
resizable = 0;
// sends data back to the function
openWinCentre(address, target_winName, width, height, toolbar, location, directories, status, menubar, scrollbars, resizable);

can anyone help?