Thanks Claus, you are a lifesaver, the formula works brilliantly, I just need to spend some time learning the Index and Match functions now.

This has thrown up one further issue though, being that if there are 2 or 3 milestones in the same week I am currently only able to show the first one. I know I can paste your formula into an array of cells to obtain multiple results but that seems only to work if the results array is a vertical one. I could really do with returning the multiple results horizontally in columns G, H and I. Is there a genius solution to this?