joining and sorting two arrays

Hi everybody,

I have one range of dates on column A that will be filled progresively (they might be repeated)

I'm trying to make a formula on another column that start with the lowest date, and on the following rows show the end of month date. If on column A there is another date prior to end of month that one should be chose instead.

For example:

Column A: 12/31/08, 03/15/09, 05/08/09, 10/28/09
Column B should show: 12/31/08, 01/31/09, 02/28/09, 03/15/09, 03/31/09, 04/30/09, 05/08/09, 05/31/09, 06/30/09, 07/31/09 and so on

I thought I could fill a temporary range calculating the end of month dates, somehow joining the two arrays, sorting them, and then output. Perhaps it can be done with an array formula but I don't know how to create it.

In case it can't be done with standard formulas a VBA custom formula could be usefull thou I don't know how to do it either.

Thanks. Paul.