What should I do if I I want the timer goes up, not going down, like in this video by Gamma.
http://www.youtube.com/watch?v=bsW6yGzPhA4

I made a script for that a long time ago. You'll have to tweak it to actually implement it in whatever you're doing though. As it is it'll just start counting up right away and won't stop.

(global short ticks 0)
(global short seconds 0)
(global short minutes 0)

(script continuous manage_ticks
	(set ticks (+ ticks 1))
	(if
		(>= ticks 30)
		(begin
			(set seconds (+ seconds 1))
			(set ticks 0)
		)
	)
	(if
		(>= seconds 60)
		(begin
			(set minutes (+ minutes 1))
			(set seconds 0)
		)
	)
	(hud_set_timer_time minutes seconds)
)

If I want to stop the timer, should I use the command that stops the timer???

(global short ticks 0)
(global short seconds 0)
(global short minutes 0)
(global boolean run true)

(script continuous manage_ticks
	(if
		(= run true)
		(begin
			(set ticks (+ ticks 1))
			(if
				(>= ticks 30)
				(begin
					(set seconds (+ seconds 1))
					(set ticks 0)
				)
			)
			(if
				(>= seconds 60)
				(begin
					(set minutes (+ minutes 1))
					(set seconds 0)
				)
			)	
			(hud_set_timer_time minutes seconds)
			(pause_hud_timer true)
		)
	)
)

Set the boolean "run" to false.

If I want to stop the timer???
What should I write if I want to stop the timer after a AI encounter is dead??

(sleep_until (= (ai_living_count [AI]) 0) 15)
(set run false)

K.