Yes, you can alter the sort order by doubling clicking. Set the sort order on form open, pass the sort (ASC or DESC) to a variable. On double click, get the value and reverse it
(If strSort = ASC then...set to DESC; If strSort = DESC then...set to ASC), reset the variable & refresh the form. As for being intuitive, colour the labels and put a small label nearby with caption "Double click green header to change sort) or something like that, as well as sending an email to users so they can ignore it
. The arrow idea is not bad - cycle an image as well.
The option group, while maybe not the best, does not have to be on this form - you can open it and return the chosen value.
So if you can/have figured out how to sort on label clicking, you should be able to do the same with your combo box. Create one with a value list and write a Select Case statement to handle the sorting? This method would allow you to provide sorting on multiple fields.