Base the report on a query. In query design view enter something like the
following (as one line) in the 'field' row of a blank column:
MyValue: Nz([Enter a value if you wish to override the default, otherwise
leave blank],"My default value")
where 'My default value' is what you want to appear if the user does not
override it. Bind a text box control in the report to the MyValue column.
When the report is opened the user will be prompted to 'Enter a value if you
wish to override the default, otherwise leave blank'. If they leave it blank
and click OK the default value will show in the text box, if they enter a
value and click OK that value will appear.
Ken Sheridan
Stafford, England