>I have two dates, a start date eg 06/06/1999 and maturity date e.g. 06/03/2000 . The scenario is I have to make valuations on dates falling back from the maturity date at intervals of three months ie. For example, on 06/03/2000, 03/03/2000, 12/03/1999, 09/03/1999. The problem is how to programmatically calculate these dates, specially if the maturity date is the 31st, and 3 months previously, the month was only 30 or 28 days long. If anyone has done anything this before could you let me know, I’d appreciate it.

Just use

GoMonth(EndDate, -nMonths*3).

If it's a 31st of February, it will fall back to 28th or 29th. Or you can calculate the average length of a quarter of a year (91.25 or 91.5 days), round to an integer and subtract that from the end date, like

EndDate-round(90.25*i, 0)