I have a table tblSequence with 3 cols in MS SQL: ID, IP, [Timestamp]

Content could look like this:

ID          IP              [Timestamp]
--------------------------------------------------
4347        62.107.95.103   2010-05-24 09:27:50.470
4346        62.107.95.103   2010-05-24 09:27:45.547
4345        62.107.95.103   2010-05-24 09:27:36.940
4344        62.107.95.103   2010-05-24 09:27:29.347
4343        62.107.95.103   2010-05-24 09:27:12.080

ID is unique, there can be n number of IP's.

Would like to calculate the average time spent per IP. in a single row

Know you can do something like this:

SELECT CAST(AVG(CAST(MyTable.MyDateTimeFinish - MyTable.MyDateTimeStart AS float)) AS datetime)

But how on earth do I find the first and last entry of my unique IP row so I can have a start and finish time? I'M stuck.

Would like to calculate the average time spent per IP. in a single row