function mascara(e,src,mask)
{
	
	if(window.event) 
		_TXT = e.keyCode; 
	else 
		if(e.which) _TXT = e.which; 
	
	if(_TXT > 47 && _TXT < 58)
	{
		var i = src.value.length; 
		var saida = mask.substring(0,1); 
		var texto = mask.substring(i);
		if(texto.substring(0,1) != saida) 
			src.value += texto.substring(0,1); 
		return true; 
	} 
	else 
	{ 
		if (_TXT != 8) 
			return false; 
		else 
			return true; 
	}

}