We have a feature in our game that loads text on the screen via a Layout change when X number of enemies are killed.
The way we set it up is:
Global number Kills = 0 (at start of Layout)
Enemy - Health <= 0 - Enemy - Destroy / System - Add 1 to Kills
System - Kills = ## - System - Go to LayoutXYZ
LayoutXYZ then displays text and Waits before going to the next Layout.
Not sure if it is the best way, or if it is even the way you are looking for, but it works for us.