function changeTipo(elem){
   $(".attribute-proveedor select").attr("disabled","disabled");
   $(".attribute-cliente select").attr("disabled","disabled");
   if(elem.value == 0) $(".attribute-proveedor select").removeAttr("disabled");
   else $(".attribute-cliente select").removeAttr("disabled");
}
function changeProveedor(elem){
   if(elem.selectedIndex == elem.options.length-1) $(".attribute-otro_proveedor").show();
   else $(".attribute-otro_proveedor").hide();
}
function changeCliente(elem){
   if(elem.selectedIndex == elem.options.length-1) $(".attribute-otro_cliente").show();
   else $(".attribute-otro_cliente").hide();
}