I have made a document full of macros and protected the cells to prevent
anyone writing over the formulae. I need to use the group function for some
of the columns in which the protected cells are, but if I set the grouping
function for the columns, once the sheet is protected, the grouping function
does not work (clicking on the plus signs doesn't reopen the columns).

It is also not possible to add the grouping function to columns once the
sheet is protected, even if only individual cells are protected.

Which of the options under Tools/Protection/Protect Sheet do I have to
select or leave unselected in order for the grouping function to work - or
does anyone have any other tips?

Thanks to anyone who can help out with this one!