validation for textbox using javascript which takes only values like 12.12 before and after dot only 2 values

function onlyDouble(evt) {
            var val1;
            if (!(evt.keyCode == 46 || (evt.keyCode >= 48 && evt.keyCode <= 57)))
                return false;
            var parts = evt.srcElement.value.split('.');
            if (parts.length > 2)
                return false;
            if (evt.keyCode == 46)
                return (parts.length == 1);
            if (evt.keyCode != 46) {
                var currVal = String.fromCharCode(evt.keyCode);
                val1 = parseFloat(String(parts[0]) + String(currVal));
                if(parts.length==2)
                    val1 = parseFloat(String(parts[0])+ "." + String(currVal));
            }

            if (val1 > 99.99)
                return false;
            if (parts.length == 2 && parts[1].length >= 2) return false;
        }