In cell A129, I have a date value.
In cell B129, I'd like to be able to show the date (in "mmm-yy" format) of
the previous June.

For example:
If A129 shows Aug-08, I'd like B129 to show Jun-08.
If A129 shows Apr-09, I'd like B129 to show Jun-08.
If A129 shows Jul-09, I'd like B129 to show Jun-09.

However, if A129 shows Jun-09, I'd like B129 to show Jun-09.

I'm trying to establish the start and end dates for the financial YTD and
the month provided.

I hope that makes sense. Any ideas?