.... So that, a click anywhere within the cell should trigger the
checkbox. I was not able to do that because the checkbox is always
placed right next to the left side of it's clickable area. If only I
could change that alignment to "middle" somehow, all my problems would
go away.

Eventually I want to do this programmatically, but manual steps are
also welcome, as I can just record a macro. This has to work in
Excel2003, so I want to use the simplest type of checkboxes available.

Many thanks.