It will be trigger_repeater.
maybe the name tells everything but let me tell you.
when you open map editor you will see in the list one trigger_repeater when you click on it...
you will see menu:
In the start you can out the name of env_Sprite, env_Object,
Func_DynWall, Gen_Weather, and etc if you know what i mean
you will see
Repeater speed (ms)
you will just type how meny ms or sec to repeat the env_Sprite, env_Object,
Func_DynWall, Gen_Weather, and etc.
if you got question just replay
ok my Question is DC can u make it?