Need help with a trigger

I need help to make this trigger: Every 30 seconds, if a certain building is in a region, various units will be created for a unit. Like in a AoS game. Please, write the nessessary events/triggers/actions so that an idiot could understand them. If someone helps me, I'll put your B. Net name in the credits, if you give it to me.

Event: Time Elapsed - Time elapsed 30 seconds
Condition: None
Action: Create Unit - Create (xx) number of (unit type) at (xxxx) region.

Just make a region around the building you're making the spawn point for.

I did that much, but, they are still created even if the building is gone. I need it so they'll never be made again if the building is gone.

Make a second trigger.

Event: Specific unit(the building in the region) dies
Condition:
Action: Turn Spawning trigger off

Thank you! What's your B. Net name, I'll add it to the credits

xXL33t-DragonXx USwest. No problem. Now if someone could help me with my trigger. :////