Hi,
Maybe something along the lines of;
var selectedCheckboxesCount = Subform1.resolveNodes('#field.[ui.oneOfChild.className == "checkButton" and $ == 1]').length;
var attachmentCount = event.target.dataObjects == null ? 0 : event.target.dataObjects.length;
if (selectedCheckboxesCount != attachmentCount)
{
app.alert("Something is missing")
}
Line 1 assumes all your checkboxes are in a subform called Subform1 and that they have the default value for true (which is 1), you may need to change these two things.
Regards
Bruce