You would need about 3 triggers to do this.
| Trigger |
null| Conditions: |
¤ Switch 1 is Set
|
| ¤ Unit X has suffered X Death Counts |
| Actions: |
¤ Create Marine
|
¤ Subtract X Death Counts to X Unit
|
| ¤ Preserve Trigger |
Basicly you would have to test how many death counts occur in 2 seconds. I believe that it's 12.2 per second.
| Trigger |
null| Conditions: |
| ¤ Switch 1 is Set |
| Actions: |
¤ Add 1 Death Count to Y Unit
|
¤ Add 12 Death Counts to Z Unit
|
| ¤ Preserve Trigger |
This trigger would be the 50 second timer. Every second a Death Count is added to Y unit.
| Trigger |
null| Conditions: |
| ¤ Death Count is 50 for Y Unit |
| Actions: |
| ¤ Disable Switch 1 |
Once you have 50 Death Counts of Y Unit, then you know 50 seconds have passed and you can disable the switch.
It's simple yet effective. Another method that i'd rather use would be having two physical timers.
Using 2 observers have one move a distance equivalent of 2 seconds and then have the other one move a distance equivakent to 50 seconds.
Then you get the overall idea, once the first observer has reached it's destination create the marine and move the first observer to it's original location and order it to move to the 2 second location.
Now with the second oberver just disable the switch once it reaches the 50 second location.
I myself would prefer using the Physical Timer because it is less buggy although it takes more time to correctly create.