Massing Units

I have a trigger for it but it does not seem to work for some odd reason
my trigger is:
If ((Number of units in (Units in Region 013<gen> owned by )Picked player))) Equal to 1) then do (Unit Group - Order (Units owned by (Picked player) of type Zergling) to Attack-Move To (Center of Region 000<gen>)) Else do (Do Nothing)

First, you have to pick a player in order to use Picked Player. I am assuming that this is a part of a larger trigger action, as in "Pick Every Player in (All Players) and do <the stuff above>"

Second, it appears that this action will only go if the player hase EXACTLY ONE unit in Region 13. I don't know what you are trying to do, but I think you may want to change "Equal to 1" to "Greater than or equal to 0".

Third, you stated that this was the trigger, but you only gave a trigger action. Make sure you have an event that sets this off too.

well im trying to make zerg blood for warcraft
still isnt working out but can anyone help me out, heres what i got

Events
-Unit A unit enters Region 012<gen>

Actions
-Unit Group - Order (Units owned by (Random player from (All players)) of type Zergling) to Attack-Move To (Center of Region 000 <gen>)

my idea is that when a unit goes to a becon that is region 012, all the zergling attack a persons spawn point that is region 000
then i also got for stopping it (on a different trigger)

Events
-Unit A unit leaves Region 012<gen>

Actions
-Turn off massing red<gen>

any ideas on making it better/helping it?

nevermind, i got it all, its working, thanks alot