Reversing Journal Entries on unknown future date

For some of our reversing journal entries, we are unsure of when the reversal will take place.  It might be in the subsequent month or a few months down the road, however the exact date is not known when the original entry is posted or when that period is closed.

Is there any way to set up a reversing entry but leave the reversal date open?  So then when you do need the reversal, you can go in an enter in the right date without altering the original entry. 

Or, is that what the 'Defer Entry' box is for?  The help manual is unclear about what this means.