First some comments on the expression. The difference between two dates is returned as a number of days. Now() returns the current time as well as the current date and can occassionally cause erroneous results if what you really wanted to use was Date(). It is better to use the DateDiff() function which allows you to expressly specify the unit of the resulting difference.
Assuming you are showing us a line of code from a form, the statement has nothing to do with whether or not the recordset is updatable. It is the query you have based the form on that is the problem. Search here and in help for updatable queries to get some idea of the problem with your query.
