How do I make a required dropdown field option not a valid selection

Sorry if this is a amature question. I am new to the Javascript "Validate Script" side of Adobe Acrobat Pro
How do I make a required Dropdown field option not a valid selection using Validate script. I have 4 Options Under Dropdown:

1. Select One (Not a valid choice)-Want to use it as a default "Title"
2. Option 1- (Valid Required Choice)
3. Option 2- (Valid Required Choice)
4. Option 3- (Valid Required Choice)

As it stands now "Select One" can be used as a choice and user can move on with out actually selecting one.

Is this a possible thing?

Ive searched all over and even tried to modify other scripts from post to try and accomplish this with zero success. 

Other post I was looking at: See Post Here

Script peices is credit to: try76 

(This is what I copied off it to try and accomplish my goal, as the full one seem unnessisary to my useage)

var f1 = this.getField("Option 1");
var f2 = this.getField("Option 2");
var f3 = this.getField("Option 3");
if (event.value=="Select One") {
    f1.readonly = true;
    f2.readonly = true;
    f3.readonly = true;
    f1.required = false;
    f2.required = false;
    f3.required = false;
}

Thanks for any help.