It's the classic "Kills to Cash" problem.
Unfortunatley you can't just do this:
| Trigger |
| Conditions: |
| ¤ Current player kills at least 1 Zergling. |
| Actions: |
¤ Display text for current player: "..."
|
¤ Modify score for Current Player: add 1 Custom.
|
¤ Set kills of Zergling to 0. (This action dosen't exist)
|
| ¤ Preserve Trigger. |
There's just no way to set the kills, it's impossible.
You're not out of luck though. There are a few other ways to detect when a player kills something.
The
Kills to Cash tutorial shows several ways of doing it.
The
Kills to Cash 'Perfect' tutorial shows a more advanced way.
A program called
SCTrigger can make the kills to cash triggers for you. It's easy and it works, but it's a "brute force" method. All it really does is make lots and lots of triggers. If you wanted to give the player 1 mineral for every kill up to 1000 kills, you could end up with 1000 seperate triggers, and once the player reaches 1000 kills he will stop getting minerals.
I recommend reading the tutorials.