AnD4D
Are the objects created and destroyed at runtime?
You could do this if the first 4 instances are controllable and the last 4 are ghost.
Sprite Boolean "ghost" is set
--- sprite set x to sprite(sprite.iid-4).x+400
Or if you just want each instance with ghost set to be at an offset you could do
Global otherx=0
Repeat 4 times
---Sprite is ghost
---pick sprite instance loopindex
------set otherx to sprite.x
---sprite is not ghost
---pick sprite instance loopindex
------sprite set x to otherx+400
Of course with that example there are 8 instances.