I don't understand what you want to do exactly.
If you set one of their positions somewhere, the ones behind it should follow it. You can also add to the for each object loop something that makes it ignore the one you want to move, if you need to.
If you want one of the objects to leave the line on it's own (or be destroyed), I guess you can set it's value to -1 or whatever then either set all the values behind it to one less than their value.
Or you could just make the one behind it temporarily always set gotox and gotoy of the one 2 ahead of it (using the same functions, with the parameter as what it was -1) then when it rejoins the line, stop that event somehow and it would go back to its original position in the line, though this wouldn't really work when destroying it.