Replacing the decimal point key (from numpad) with correct decimal separator (in silverlight!)

void Cell_KeyDown(object sender, KeyEventArgs e)
{
     if (e.Key == Key.Decimal)

void CellText_KeyUp(object sender, KeyEventArgs e)
    {
        var DecSep = System.Threading.Thread.CurrentThread.CurrentCulture.NumberFormat.NumberDecimalSeparator;

        if (e.Key == Key.Decimal && DecSep != ".")
        {
            if (e.OriginalSource is TextBox)
            {
                var TB = (TextBox)e.OriginalSource;
                string sText = TB.Text;

                int iPos = TB.SelectionStart - 1;
                if (iPos >= 0)
                {
                    System.Diagnostics.Debug.Assert(sText.Substring(iPos, 1) == ".");

                    TB.Text = sText.Substring(0, iPos) + DecSep + sText.Substring(iPos + 1);
                    TB.SelectionStart = iPos + 1; // reposition cursor
                }
            }
        }
    }

<html>
<heaD>
<script language="javascript">
function keypress1 ()
{
 var e=window.event || e
 unicode = e.charCode ? e.charCode : e.keyCode;
 if (unicode==46)
   { return (e.charCode ? e.charCode=44 : e.keyCode=44); }
}
function keypress2 ()
{
 var e=window.event || e
 unicode = e.charCode ? e.charCode : e.keyCode;
 if (unicode==46)
   { return (e.charCode ? e.charCode=46 : e.keyCode=46); }
}
function keyDown(e){
 if (!e){
   e = event
 }
 var code=e.keyCode;
 if(code==110)
   return document.onkeypress=keypress1
 else if(code=188)
   {  document.onkeypress=keypress2 }
}
document.onkeydown = keyDown
</script>
</head>
<body>
<input type=text>
</body>
</html>

public class NumericUpDown : System.Windows.Controls.NumericUpDown
{
    [DebuggerStepThrough]
    protected override double ParseValue(string text)
    {
        text = text.Replace(".", Thread.CurrentThread.CurrentCulture.NumberFormat.NumberDecimalSeparator);
        return base.ParseValue(text);
    }
}