@Sray-Audic you can do that with something like this:
self.PowerupSelected = whichPowerUp();
if(self adsButtonPressed())
powerup = level specific_powerup_drop(self.PowerupSelected, self.origin);
whichPowerUp()
{
powerups[0] = "nuke";
powerups[1] = "insta_kill";
powerups[2] = "double_points";
powerups[3] = "full_ammo";
return powerups[ randomInt(powerups.size) ];
}