This is what I would do.....
1. Set up a Global Variable under File>>Form Properties>>Variables Tab
//Variable declared here are always considered string
Example: GCheckCount and set the initial value 0
2. For each CheckBox I would add the following code under "change" event
if (this.rawValue == 1) {
GCheckCount.value = "" + GCheckCount.value + 1;
}else {
GCheckCount.value = "" + GCheckCount.value - 1;
}
3. Also for each CheckBox I would add the following code under "docReady" event to get the initail count
if (this.rawValue == 1) {
GCheckCount.value = GCheckCount.value + 1;
}
4. When you validate do the following
if (GCheckCount.value == "0") {
app.alert("Please select one or more checkboxes.");
}