Using <* works fine in an Advanced Filter when the field searched is TEXT,
but it does not work on numbers or dates. What's a good way of writing an
Advanced Filter that looks for blanks in a column with dates or numbers?

Examples:
Data range is like this:

TEXT NUMBER DATE
A 1 8/21/06
B 8/20/06
3 8/19/06
D 4

If Advanced Filter is TEXT <* then you get that third row -- the one with
the blank. BUT, if the Advanced Filter is NUMBER <* you get all records.
Same is true for the DATE column.