function isNumberKey(evt)
 {
	var charCode = (evt.which) ? evt.which : event.keyCode
	if (charCode > 31 && (charCode < 48 || charCode > 57))
	{
		return false;
	}
	return true;
 }

function checkDigit(evt)
{   
   var charCode = (evt.which) ? evt.which : event.keyCode
	var element = evt.srcElement.name;
	var elemValue = document.getElementById(element).value;
    if(charCode == 13)
		{
		return false;
		}
	if(charCode == 48)
	{
		var selectedText = document.selection.createRange().text; 
		if (elemValue == null || elemValue == '') {
			return false;
		} 
		else {
			if (elemValue.length == selectedText.length)
			{
				return false;
			} 
			else {
				if (selectedText.length > 0)
				{
					if (elemValue.substr(0,selectedText.length) == selectedText)
					{
						return false;
					}
				}
				else
				{
					return true;
				}
			}							
		}									
	}
	else
		return isNumberKey(evt);
}