Click on part of an input field

<html>
<head>
<title></title>
</head>
<body>
<script type="text/javascript">
    var tempX = 0;
    var tempY = 0;

    document.onmousemove = getMouseXY;

    function getMouseXY(e) {
            tempX = e.pageX;
            tempY = e.pageY;

            // catch possible negative values in NS4
            if (tempX < 0){tempX = 0}
            if (tempY < 0){tempY = 0}

            // show the position values in the form named Show
            // in the text fields named MouseX and MouseY
            document.getElementById('MouseX').value = tempX;
            document.getElementById('MouseY').value = tempY;
            return true;
    }

    function search(){
            // position of input field
            var distanceFromTop = 60;
            var distanceFromLeft = 8;

            // size of input field
            var inputWidth = 204;
            var inputHeight = 20;

            // size of picture
            var pictureWitdh = 20;

            // dont need to check mouse position on axis y
            // because onclick event already is on input field

            // check mouse position on axis x
            if(tempX > (distanceFromLeft+inputWidth-pictureWitdh)){
                    alert('Did click on the right');
            }
    }
</script>
<input type="text" id="MouseX" value="0" size="4"> X<br>
<input type="text" id="MouseY" value="0" size="4"> Y<br>
<input type="text" id="search" onclick="search(this)" />
</body>
</html>