I am trying to find a formula to give me the Previous Quarter End. The
headers on the spreadsheet look as follow:

Acct # Curr Period Prev Qtr End Prev Period Curr Period Prev Yr
2134 007 ? 006 007 / 2006

The report is refreshed frequently, but here is a sample of how the data
format that is populated for the date fields.

Period: 007.2007
Year: 2007

There are 12 periods in the year and 4 quarter ends (The quarter end are
March, June, September, and December)

I have formulas for all the fields except the previous quarter end (12 /
2006, 003 / 2007, 006 / 2007, 009/2007). In the example above, the previous
quarter end date would 006 / 2007.

Any clues.