Hi,
Sorry for the delay. Been a bit busy.
OK, I am assuming that your headers are in Row 1 and that your data starts
in Row 2. If this is not so, you will have to change all the 2's for whatever
row your data does start in. I have also assumed that 'Date In' is Column C
and 'Price' is Column D.
Remember to format Columns E, G, I as Date, before entering the formulas.

Row 2 of Date+30 Column: =IF(C2="","",C2+30)
Row 2 of Price-10% Column: =IF(D2="","",D2-(D2*0.1))
Row 2 of Date+60 Column: =IF(C2="","",C2+60)
Row 2 of Price-20% Column: =IF(D2="","",D2-(D2*0.2))
Row 2 of Date+90 Column: =IF(C2="","",C2+90)
Row 2 of Price-30% Column: =IF(D2="","",D2-(D2*0.3))

Ok, now select E2:J2 and fill down as far as you want.
Let me know if this is what you need.
Regards - Dave.