does anyone know if the function Lookup_Thread works if the id passed as the second input is not a boundary id but a surface id? Thanks

No for this macro, the id should be a face thread or cell thread. Postprocessing surfaces cannot accessed using this macro.

Is there any macro that accesses the postprocessing surfaces? I don't think so, but it will be really useful to my work.

I am not sure what you wish to do? You can create a edge/face in Gambit and name it as interior. Lookup thread can be used on it.

yes i know, the fact is that i have to put something like 30 sphere surfaces and meshing all the volumes in gambit is a great lost of time. If exists a function that returns a pointer to the faces of a postprocessing surface I'll be able to export without changing the mesh.

With out UDF you can export the values on the post processing surfaces using exporting the reqd data as ASCII

file - export - ascii

thanks guys I solved the problem, anyway I guess exporting in ascii is the only way.. not the fastest