function mascara(campo, mask, e)//mascara(this,'##/##/####',event)
{
	campo.maxLength=mask.length;
    
	var src=campo.value.length;
    var mask=mask.substr(src,1);
    
    if(window.event)
    {
	    if(e.keyCode!=13 && (e.keyCode>47 && e.keyCode<58))
	    {
	    	if(mask!='#' && src>=0)
	    	{	
	        	campo.value+=mask;
	    	}
	    }
	    else
	    {
	    	e.keyCode=0;
	    }
    }
    else
    {
    	if(e.which!=13 && (e.which>47 && e.which<58))
	    {
	    	if(mask!='#' && src>=0)
	    	{	
	        	campo.value+=mask;
	    	}
	    }
	    else if((e.which>64 && e.which<91) || (e.which>96 && e.which<123))
	    {
	    	e.preventDefault();
	    }
    }
}