I have the following situation:

Fall semester:
This year, if the account start date (Acctstrt) is equal to or greater than
09/01/2008 and the account stop date (Acctstop) is less than or equal to
01/15/2009 this is considered fall

For the spring we should consider anything with an Acctstrt date greater
than or equal to 1/15/2009 and an Acctstop date of 5/31/09.

Summer semester:
There may be some summer appointments in the system already (probably only
for the sciences and psychology), if there are the Acctstrt date should be
06/01/2009 and the Acctstop date should be 8/31/2009.

How do I build a formula to recognize this?