how are you currently trying to trigger the spawns? it should be something as simple as checking a variable, say NextSpawn, which you would initialize at the start of each level and check each time the player scores and update appropriately. pseudo:
if CurrentScore => NextSpawn
SpawnBall
NextSpawn = CurrentScore + WhateverScoreIncrement
endif
hope that helps
edit: you stated "as time goes" by in the title so just incase you want the score AND the time to dictate when the next ball spawns:
if CurrentScore => NextSpawn and NextTime <= Timer()
SpawnBall
NextSpawn = CurrentScore + WhateverScoreIncrement
NextTime = Timer() + WhateverTimeIncrement
endif
i know you asked for "no code" but i think this pseudo explains it best.
by the way, the screenie looks nice!
wanted to add that the code above adds the increment to the CurrentScore and i don't know your scoring system (ie, if the score can exceed the trigger score or not, hence the "=>") but if you wanted it to trigger, say every 10 points, you could change the line:
NextSpawn = CurrentScore + WhateverScoreIncrement
to
NextSpawn = NextSpawn + WhateverScoreIncrement
