Yes, the same "checkbox" solution could be used by writing a custom cell
renderer which adds a checkbox to every cell, but it's probably too much
trouble.

   What you could do is add a boolean field for every column in your table
model which indicates whether a given column in a particular row was
selected, and then add mouse listeners to detect clicks, toggling this
boolean field.

   But maybe it's better to take a step back and think about why you need
to select individual cells, and why CTRL is not a viable option.

   - Oliver