Sorry, I would have linked to instructions, but I was in a hurry and had to run.
Open the subhood in SimPE (it's in your Neighborhoods/N00x folder, called N00x_Vacation00x.package, you'll be able to identify the correct one by lot the descriptions), go to the Lot Description (LTXT) of the secret lot and add 10 (0x00000010 actually, it's hex, but unless you encounter letters it doesn't matter) to the number in the U0 field (23+10=33, not 2310 btw).
Commit, save, woosh!
Open the subhood in SimPE (it's in your Neighborhoods/N00x folder, called N00x_Vacation00x.package, you'll be able to identify the correct one by lot the descriptions), go to the Lot Description (LTXT) of the secret lot and add 10 (0x00000010 actually, it's hex, but unless you encounter letters it doesn't matter) to the number in the U0 field (23+10=33, not 2310 btw).
Commit, save, woosh!
I have been looking for a way to do this. Thanks! Can you provide a link to your instructions as well?