You probably need to be a bit more specific with your question: e.g. do you want to count-down in seconds or simply at the framerate?

As for the logic: I suspect you're over-complicating things, though it might depend on how 'trigger' is assigned a value.  This may help a little:

1. int trigger = 0;
2. // value to count-down from
3. int count = 10;
4. void setup() {
5.  
6. }
7. void draw() {
8.   if(trigger == 1 && count > -1) {
9.     println(count);
10.     count --;
11.   }
12.   // don't use delay unless you really have to
13.   // I'm just using it here so you have time to interrupt the countdown
14.   delay(500);
15. }
16. // simluate the trigger event
17. void keyPressed() {
18.   trigger = 1;
19.   // to reset the count, just reset the variable to the start value
20.   count = 10;
21. }

thanks a lot blindfish, this is what I´m looking for, but how can I count with miliseconds instead with a delay?

1. int trigger = 0;
2. // value to count-down from
3. int count = 10;
4. // variables used for timing
5. int startTime;
6. int interval = 1000; // i.e. 1 second
7. void setup() {
8.  
9. }
10. void draw() {
11.   if(trigger == 1 && count > -1) {
12.     // check that the set time interval has passed
13.     if(millis() >= startTime + interval){
14.       println(count);
15.       count --;
16.       startTime = millis(); //reset timer
17.     }
18.   }
19. }
20. // simluate the trigger event
21. void keyPressed() {
22.   trigger = 1;
23.   // to reset the count, just reset the variable to the start value
24.   count = 10;
25. }

thanks a lot!