interval = 10; // seconds
frames = 5;
nextTime = getTime() + interval*1000;
for (i=0; i<frames; i++) {
    run("QT Capture", "grab");
    wait(5000);
    selectWindow("Captured Video");
    if (i==0)
        run("Rename...", "title=Stack");
    else {
        run("Select All");
        run("Copy");
        run("Close");
        selectWindow("Stack");
        run("Add Slice");
        run("Paste");
     }
    while (getTime()<nextTime)
        wait(1);
    nextime += interval*1000;
}