Ok... heres what I need:

column A1 contains the date the letter was sent
column A4 contains the date we received a response

I need column A3 to automatically calculate the # of days until we receive a
response.

Here is the criteria:

Must update based on function Today() so that we always have an updated # of
days and once we receive a response I need it to stop calculating and freeze
at the last number calculated. At the same time, if we haven't sent a letter
I need the space to be blank.

Is this possible? If so, does anyone have any ideas as to what might work??