TEST<script type="text/javascript">
    function minimum()
    {
        var reg = /^\d+$/g;
        var v = document.getElementById("texty").value;
        
        if (!reg.test(v))
        {
            alert("Quantity must be in numeric form.");
            document.getElementById("texty").value = 15;
        }
        
        if (v < 15)
        {
            alert("The minimum quantity on this product is 15 items.");
            document.getElementById("texty").value = 15;
        }
        
    }
</script>

<form>
    Text Box Items: 
    <input type="text" id="texty" name="texty" onblur="minimum();">
</form>