Feral Spirit alike

I created a spell base of 'Dard Portal' of Archimonde in order to create permanent summons that gives corpse. But I forgotten that these summons can be 'stored' and causes inbalance to the map. Is there anyway that I can restrict the amount of summons using triggers? Just like Feral Spirit, Misha and Pheonix where only one can be present.
Note: I added the tome of retraining also.

Thanks in advance for those who spent some effort in reading and trying this.
:foot:

Describe the spell in more detail. Tell us just exactly what the spell is creating and how many of then. I can think up a trigger, but I'll need to have the numbers...

well the create corpse thing can be on any unit its a field on the unit editor so you could give feral spirit a corpse or skeletons and stuff like that, the longest time you can set the summon timer in 1 hour I think, isnt that good enough?

Change the corpse settings of the summoned unit, and change the spell duration to 0. That should solve your problem.

If that dont help heres my trigger from my diablo rpg to handle the leveling up of my raise skeleton abilty to get more and more per level

E:unit spawns a summond unit
C: summond unit equal to (your unit)
C: # of units ownd by owner of summond unit of type (your unit) equal to (the limit u want)
A: kill summond unit

Actually, its a preset spell, I used it to create permanent units, just that I dont want too many of time in game at one time.

Its like this, for lvl 1 - 3, it summon a unit(permanent) that have feral spirits, meaning more summons(time-limited) can be retrieve from that unit. but at lvl 4
random number of units(permanent) are called, and one of the random units have 'Ancestral Spirits', that always the other random unit(permanent) thats called to be revived from its corpse.

These amount of units(permanent) actually did pretty well for the effect i wanted, but the bad side is, once the cooldown of that spell finished, i can call up one more, meaning the number of summons(time-limited) is doubled. I dont want that to happen.

For the corpse thing, I did change the setting for the summons, but the spell at level four, it actually summons two different units, which only the 'Dark Portal' , 'Spirit of Vengeance' and 'Raise Dead' allows, and out of these three, two requires corpse.

Lvl1 - one unit
Lvl2 - one unit(different and stronger)
lvl3 - one unit(different and stronger)
lvl3 - 2 - 5 random units(only two different kind) one doesn't have any abilities except can be revived by Ancestral Spirit which the other has.