Need help with formula

[Potatomr]

Hi all,

I need help with a formula, and I'd be super happy if somebody could help me. I have explained the issue in the table below. Maybe it's possible to have a macro or similar that can "go through" the file and automatically correct the dates? What's the best solution you think? The output should be the same as below - but with the correct dates. Thanks on beforehand!

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Line	FIRSTNAME	LASTNAME	ORDERID	DATE
1	Albert	Albertson	1000	2017-11-01
2	Albert	Albertson	1500	2017-11-01
3	Albert	Albertson	1500	2017-11-01
4	Bob	Bobson	1000	2017-11-04
5	Bob	Bobson	1000	2017-11-06
6	Bob	Bobson	1500	2017-11-04
7	Cat	Catson	1500	2017-11-07
Issue: If FIRSTNAME+LASTNAME has made an order with the same ORDER ID on the same DATE (like line 2 and 3), then postpone DATE by +1 for one of the lines, for example for line nbr 3. Also, if possible: Postpone DATE by +1 for Line nbr 3 UNLESS the FIRSTNAME+LASTNAME have placed an order on the +1 day with the same ORDER ID - if so then plus +2 days,

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[Potatomr]

Thank you very much, got it working!