Retaining value from a formula if new result becomes in error

[See attached file as an example]

I want to be able to manage an auto count of items in a spreadsheet based on the current date. This I can do:

[A1]
=today()

[A3]
22/09/2010

[B3]
=if(A1=A3,countif(range,criteria)


Problem
I would also like to have a history of counts. My issue is having making this an automated exercise.

[A4]
22/09/2010
[A5]
23/09/2010
[A6]
24/09/2010


[B3]
=if(A1=A4,countif(range,criteria)
[B4]
=if(A1=A5,countif(range,criteria)
[B5]
=if(A1=A6,countif(range,criteria)

Issue
When a new date occurs, I loose the previous value. Is there some automated way to retain this value before it goes into error?