The Forum Guidelines tell you not to cross-post in multiple forums, so please don't do that.
It's not that clear what you want - but can't you just do shift-left mouse click to add onto the selection one at a time, and then geGetSelSet() will return the objects in the order you want. If you want to get info about the selected instances, you could do:
or if you wanted to get the instance name, w and l properties, you could do:
instInfo=foreach(mapcar inst geGetSelSet() list(inst~>name inst~>w inst~>l))
In my case, that returns:
(("NM11" "1.2u" "280n")
("NM10" "1.2u" "280n")
("NM7" "1.2u" "280n")
("NM6" "1.2u" "280n")
which was the order I selected them in.