Put the same field on your layout, formatted as text, not as checkbox. Make it several lines high and place it next to your checkbox-formatted field. Now look what happens when you select or deselect options.
Thx! I tried a whole bunch of delimiters, but didn't think of that one!
List ( "A" ; "B" )
is another option that can be used.
List ( CheckboxField ; "B" )
will select value "B" while leaving other boxes selected.
but in such cases,
If ( IsEmpty ( FilterValues ( CheckBoxField ; "B" ) ) ; List ( CheckboxField ; "B" ) ; CheckBoxField )
is even better as it avoids selecting the same value twice.