Converting Check Boxes into a number

You can use this code as the custom calculation script of the field where you want to display the result:

var total = 0;
for (var i=1; i<=30; i++) {
    var fname = "Check Box "+i;
    var f = this.getField(fname);
    if (f==null) {app.alert("Error! Can't find: " +fname); continue;}
    else if (f.valueAsString!="Off") total++;
}
event.value = total;