my $lastcountry = '';
my $totaldowntime = 0;
while (my $row = $sth->fetch()) {
    (..., $country, $downtime, ...) = @$row;
    $totaldowntime += $downtime;
    if ($country ne $lastcountry) {
         # note this will be true first time thru the loop
         print $totaldowntime;
         $totaldowntime = 0;
         next_page();    # however you accomplish this in your setting
    }