Creating a trigger to spawn mobs when player enters area?

[AlphaWoIF]

Hi i will try to be brief.

 

Put simple i have created a hole in the ground and i want to to spawn some of my custom monsters from it when the player gets to close.

There is 2 types of monsters and i want to spawn the weaker ones first and then spwan the stronger ones when a set number of the weaker ones have been slain.

Somebody pls point me in the right direction.

Edited August 19, 2012 by AlphaWoIF