JQuery : How to disable mouse move vertically?

Question

I am creating elements selector with mouse click event. JSFiddle link. You can click on one cell and drag as you want (green color will show) . My question is how to disable mouse is moving vertically while click and drag ? Users should be only draggable horizontally. Below is my efforded codes.

HTML

<div id="grid">
                <div class="gridHeader">
                    <span><label>#</label></span>
                        <span><label>01</label></span>
                        <span><label>02</label></span>
                        <span><label>03</label></span>
                        <span><label>04</label></span>
                        <span><label>05</label></span>
                        <span><label>06</label></span>
                        <span><label>07</label></span>
                        <span><label>08</label></span>
                        <span><label>09</label></span>
                        <span><label>10</label></span>
                </div>
                    <div class="gridRow">
                        <span><label>Room #01</label></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                    </div>
                    <div class="gridRow">
                        <span><label>Room #02</label></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                    </div>
                    <div class="gridRow">
                        <span><label>Room #03</label></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                    </div>
                    <div class="gridRow">
                        <span><label>Room #04</label></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                    </div>
                    <div class="gridRow">
                        <span><label>Room #05</label></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                    </div>
                    <div class="gridRow">
                        <span><label>Room #06</label></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                            <span class="item"></span>
                    </div>
            </div>

CSS

#grid {

}
.gridHeader {
}
#grid .gridHeader > span {
    border:1px solid black;
    text-align: center;
    padding: 3px 5px;
    margin-top: 1px;
    display: inline-block;
    width: 16px;
    vertical-align: middle;
    margin-right: -3px;
    background-color: silver;
}
#grid .gridHeader > span:FIRST-CHILD {
    width:75px;
}
.gridRow {
}
#grid .gridRow > span {
    border: 1px solid black;
    text-align: center;
    padding: 3px 5px;
    margin-top: 1px;
    display: inline-block;
    width:16px;
    height:20px;
    vertical-align: middle;
    margin-right: -3px;
}
#grid .gridRow > span:FIRST-CHILD {
    width:75px;
    background-color: silver;
}

Scripts

$(document).ready(function(){
    $('#grid .item').mousedown(function(){
        $(this).attr("style", "background-color:green");
        $('#grid .item').mouseenter(function(){
            $(this).attr("style", "background-color:green");
        });
    });
    $('#grid .item').mouseup(function(){
        $('#grid .item').unbind('mouseenter');
    });
});

Answer 1

You don't need to block the vertical mousemove . You just need to catch the proper element and its siblings and also attaching event each to class where the items are placed as below:

DEMO

$(document).ready(function(){
        $('.gridRow .item').mousedown(function(){
            $(this).attr("style", "background-color:green");
            $(this).siblings().mouseenter(function(){ 
            //^^^^style only its siblings where mouse has been clicked
                $(this).attr("style", "background-color:green");
        });
    });
});