Series of formulas needed to fill in all matching criteria based on a drop-down by month.

In the attached spreadsheet:

Under the "Summary" sheet I would like to be able to change the month from the drop-down in A1 (already there, in yellow), and for A4 and below (Orange) to populate the Unique ID's that match based on the months from "Data".

For example, when January is selected in A1, I would like for all the Unique Id's grouped by the month January in the sheet "Data" to list out. For January there would be 11, but it will vary from month to month.

If possible, I could still really use help with this formula. Based on my limited knowledge it will need a CSE formula, and possibly some Index and Match, but I can't figure out how to consistently get a set of values to return, I usually just get one.

Thanks for any solutions.

Maybe this is too difficult for all the gurus out there???