If you want to do this for every value in the field then

UPDATE YourTable
SET YourField = Null

In query design view
== Add the table
== Add the field to the field list
== Select Query: UPdate from the menu
== In the UPDATE TO under the field enter
Null
== Select Query: Run from the menu

As usual consider backing up the data BEFORE you run the query. You cannot
recover from this without a backup.

John Spencer
Access MVP 2002-2005, 2007-2009
The Hilltop Institute
University of Maryland Baltimore County

golfinray wrote:
Users have mistakenly entered data in a field where we did want them to enter
any data. We just want to set the field back to blank or null, not zero.
Thanks!