$warnlevel = $Win32::OLE::Warn;
$Win32::OLE::Warn=1;
$done = 0;
while ($done == 0) {
    if ($excel->ActiveWorkbook) {
        sleep 15;
    } else {
        $errmsg = Win32::OLE->LastError;
        if ($errmsg =~ m/busy/) {
            sleep 15;
        } else {
            $done = 1;
        }
    }
}
$Win32::OLE::Warn=$warnlevel;