At the moment box 4 remains ticked if 1, 2 or 3 are deselected.I've tried options on the net and the code at the moment is if (event.target.value!="Off") this.getField("TICKBOX4").checkThisBox(0, true); but I can't work how to automatically untick box 4 if any of the other 3 are unticked. Any help would be appreciated and I suspect this is quite straightforward if you know what you're doing!!!
After that line of code add this line:
else this.getField("TICKBOX4").checkThisBox(0, false);
Works a treat and really appreciated, thank you!!!