One way to do it would be to add an instance variable to the object (Can't think of a good name so I just used 'B') and an event with the system condition:
"for each object by order of Object.RandomValue ascending"
--> set object.B to loopindex
This will number each object.B by the order in which it was picked. going from 0,1,2,3 .. etc
Then in a separate event, to pick the highest, you can do
Object.loopID = object.count-1
-->set scale to... etc
the -1 is necessary because the 'loopindex' expression is 0 based (0,1,2,3..), but the 'count' expression isn't (1,2,3,4..)