Need Action Script Help

Hi, I’m making a Flash 8 game and I need a little help with action script. Ill explain a bit the game so you can understand.

In the game, you have to shoot different enemies that appear in the screen. To shoot, you just have to click, and here is my first problem:
I want to play a sound each time you click, so when you click you’ll hear a shoot.

Sometimes, I want to wait for the player to kill the current enemies before new enemies come, that’s just to make the game a bit easier, and it’s useful in the beggining.
So, I have another problem:
On the scene 2 (the beging of the game), I set a global variable (so I can use it in different scenes) called “enemies”, so I write this on the first frame:

_global.enemies = 0;

And the enemies are movieclips, so in the first frame of each movie clip I want to put a code that adds 1 to the variable, but I dont know the code to do it.
It would be something like _global.enemies+1 but I am not sure. And later, I need a code that would be something like _global.enemies-1 that goes in the movie clip, on the frame that the enemy dies.

But thats not enough, back to the scene 2, I need to make an If sentence, that says something like “If _global.enemies=0 gotoAndPlay(2)” (number 2 is an example).

Please help me with these codes, if you cant answer to all my questions, tell me what you know, everything is helpful!

Thanks!

PS: Sure I’ve made some mistakes, because English is not my native language.