Code:
  set %timeremaining 10
  rline @PRE-TIME 4 This window will close in 10 seconds
  .timer 10 1 dec %timeremaining $chr(124) rline @PRE-TIME 4 This window will close in $!eval(%timeremaining,2) seconds $chr(124) if ( $!eval(%timeremaining,2) == 0 ) { window -c @PRE-TIME }
Here's the script I tested it with...
Code:
alias PRE-TIME {
  window @PRE-TIME
  aline @PRE-TIME Line1
  aline @PRE-TIME Line2
  aline @PRE-TIME Line3
  aline @PRE-TIME Line4
  set %timeremaining 10
  rline @PRE-TIME 4 This window will close in 10 seconds
  .timer 10 1 dec %timeremaining $chr(124) rline @PRE-TIME 4 This window will close in $!eval(%timeremaining,2) seconds $chr(124) if ( $!eval(%timeremaining,2) == 0 ) { window -c @PRE-TIME }
}
Messy, but works..