I would recommend using a button, not a check-box for this. It can be confusing for the user if the "ALL" box is checked, but not all the boxes that are connected to it are, or if they uncheck that box, and the others don't uncheck with it, for example.
To do it with a button use this code as its Mouse Up event:
var fieldsToCheck = ["CB1", "CB3", "CB4", "CB7"];
for (var i in fieldsToCheck) this.getField(fieldsToCheck[i]).checkThisBox(0, true);
Edit the fieldsToCheck array so it contains the actual fields for each button, for course.
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