Disable the previous and next options in a select box?

Is this possible? Say someone selected a select option, is there a way to disable the previous (if available) and next (if available) option to the their selected one?
Ofc it'll need to use a 'onChange' trigger, but I'm not sure how to do the function part.

Any ideas?

 

So you want a JS function that disables other option tags when selected? Well there are a couple ways you can do that, but I'll out line the idea that came to my head;

<!-- HTML SIDE -->

<select id="selectBox1" onchange="onSelectChange(this.id,this.value);" >
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>

HTML:

// JS SIDE //

function onSelectChange(targetElement, newValue){
	if(newValue = "3"){
		runDisableOption(targetElement, 0);
		runDisableOption(targetElement, 3);
	}

	if(newValue = "1"){
		runEnableOption(targetElement, 0);
		runEnableOption(targetElement, 3);
	}
}

function runDisableOption(targetSelect, targetNode){
	var optionNodeArray = document.getElementById(targetSelect).childNodes;
	optionNodeArray[targetNode].disabled = true;
}

function runEnableOption(targetSelect, targetNode){
	var optionNodeArray = document.getElementById(targetSelect).childNodes;
	optionNodeArray[targetNode].disabled = false;
}

Code (markup):

Or something along those lines, I haven't tested the code- so it's just theory. . .

 

Thanks.... I forgot to say its a multi-select box, will this theory still work?

I've attached a screenshot to show that some options are disabled already (by default (by PHP)) so I do not want those disabled options to be enabled again - if you get me.