So I just tried this and it still only picks up the dates for the old site. I guess because there is data in B3 (i.e. it's not blank), the IF statement doesn't work for what I need it to do because it doesn't know to move onto A3 when there are no more dates left for B3, yet there are dates for A3.

The more I think about this the more I really don't know if this is possible