You may find what you need he
http://www.mcgimpsey.com/excel/timestamp.html
The section using circular references shows that exact case.

Hope this helps,
Miguel.

"JDay" wrote:

If anything appears in cell A1, I would like the date to appear in cell B1.
However, once that date appears, I want that date to remain constant, not
update daily. I need to know what date I sent a particular letter so the
date must remain.