function CheckNumeric( field )
{
	var thisField = field.value;
	var validChars = "0123456789-/";
	var strChar;
	var result = true;
	
	if (thisField.length == 0) return false;
	
	for (i = 0; i < thisField.length && result == true; i++)
	{
		strChar = thisField.charAt(i);
		if (validChars.indexOf(strChar) == -1)
		{
			result = false;
		}
	}
	if( result == false )
	{
		alert("Must be a numeric value.");
		return false;
	}
	else return true;
}