Adding Conditional to a Dimension

[Rosiered]

Hi,

I need some help to add a condition to a field base on if the data matches the line above in another field. 

So if Reservation Number matches the line above then minus the collection date by one day otherwise keep the original collection date.

So far I have 

IF([Reservation] = Above([NewCollection] -1, [NewCollection])

Just to add to bare in mind I have already added to the script if the collection date is greater than stay say 'Still Open' will doing this condition effect that? 

[Rosiered]

Sorry that is meant to say greater than Today in the last sentence 

[Brett_Bleess]

Would likely be best if you can attach QVW on this one, as I think folks will need that to check things over and be sure that what you want fits what you are saying you have tried, without that, not sure anyone will really be able to say for sure.

Regards,
Brett