// ATTENZIONE !!!
// dipende dal file prototype.String.trim.js
String.prototype.isNumeric = function()
{
	if (this.trim() == "")
		return false;
	
	var ValidChars = "0123456789";
	var isNumber=true;
	var Char;
	var i = 0;
	
	while (i < this.length && isNumber)
	{
		Char = this.charAt(i); 
		if (ValidChars.indexOf(Char) == -1) 
			isNumber = false;
		i++;
	}
	return isNumber;
}