You probably could do it by adding a record somewhere with the ALL value, and triggering macro code any time the selections in that field are changed, and having the macro check if the field value was ALL, and if so select all values.
But why do you want this feature? If you don't select anything, that's pretty much equivalent to selecting everything. So have the users clear the field by one of the many ways of doing that, and that's basically like selecting ALL. Or if they MUST for some reason be able to select all the values, train them to right click and then click on select all. Or if you want a one click solution, I suppose you could add a button to select all of the values, but I prefer that my users get used to the default QlikView controls, since those will work in EVERY QlikView application.
Or am I completely misunderstanding what you're after?
