Formular "Wenn Feld aktiviert, dann wird ein andres Fled Pflichtfeld"

You can run a script to count the check boxes that are already selected and if there are already 5, the 6th will not check.  However, you should add an alert so you don't drive users crazy trying to figure out why they can't select a 6th.  Assume 10 check boxes named "Check Box.0" through "Check Box.9".  Add the following mouse up action to each check box before the original scrip:

var count=0;
for(var i=0;i<10;i++)
{
if(this.getField("Check Box."+i).value!="Off")
{count++}
}

if(count>5)
{
app.alert("You have exceeded 5 check boxes.  Please uncheck one.",1);
event.target.value="Off";
}