//browser detection
var strUserAgent = navigator.userAgent.toLowerCase();
var isIE = strUserAgent.indexOf("msie") > -1;
var isNS6 = strUserAgent.indexOf("netscape6") > -1;
var isNS4 = !isIE && !isNS6  && parseFloat(navigator.appVersion) < 5;

//regular expressions
var reValidChars = /[0-9.]/;
var reValidString = /^\d*.{0,1}\d{0,2}$/;
var reKeyboardChars = /[\x00\x03\x08\x0D\x16\x18\x1A]/;
var reClipboardChars = /[cvxz]/i;

//mask functions
function maskKeyPress(objEvent) {
    var iKeyCode, strKey, objInput;

    if (isIE) {
        iKeyCode = objEvent.keyCode;
        objInput = objEvent.srcElement;
    } else {
        iKeyCode = objEvent.which;
        objInput = objEvent.target;
    }

    strKey = String.fromCharCode(iKeyCode);

    if (isValid(objInput.value)) {
        objInput.validValue = objInput.value;
        if (!reValidChars.test(strKey) && !reKeyboardChars.test(strKey) && !checkClipboardCode(objEvent, strKey)) {
            //alert("Invalid Character Detected!\nKeyCode = " + iKeyCode + "\nCharacter =" + strKey);
            return false;
        }
    } else {
        //alert("Invalid Data");
        objInput.value = objInput.validValue;
        return false;
    }
}

function checkClipboardCode(objEvent, strKey) {
    if (isNS6)
        return objEvent.ctrlKey && reClipboardChars.test(strKey);
    else
        return false;
}

function isValid(strValue) {
    return reValidString.test(strValue) || strValue.length == 0;
}

function maskChange(objEvent) {
    var objInput;

    if (isIE) {
        objInput = objEvent.srcElement;
    } else {
        objInput = objEvent.target;
    }

    if (!isValid(objInput.value)) {
        //alert("Invalid data");
        objInput.value = objInput.validValue || "";
        objInput.focus();
        objInput.select();
    } else {
        objInput.validValue = objInput.value;
    }
}

function maskPaste(objEvent) {
    var strPasteData = window.clipboardData.getData("Text");
    var objInput = objEvent.srcElement;

    if (!isValid(strPasteData)) {
        //alert("Invalid data");
        objInput.focus();
        return false;
    }
}