you cant.
It is in the school.
Greg's locker is 7 from Holly Hill's and is 5 from Chirag Gupta's.
you look for the locker that is different then the others :-D
Open Greg's locker.
Open Greg's locker.
you go to greggs locker
5th lockers from the broken locker go to the right
His locker combination is 9-37-15.
Supposedly, according to Greg's journal, Holly's is 2 from Chirag's, which is broken, which would make hers the 1st (leftmost) or 5th of the 9 lockers under the School Spirit banner. But Greg's locker (#8) is either 3 or 7 from hers, not 5 as it was supposed to be. He is 5 from Chirag's. Obviously a case of misinterpretation by one of the creative staff.
In Greg's locker>
9 37 15
type in 9 37 19