Very interesting code indeed - thank you very much for this.

Some comments:

1. code to drop global temporary table ##Tree has no effect (end of TRY block and in CATCH block)...

Yes, Tom,

Thanks for pointing out the problems with Microsofts built-in stored procedures.

If the OPENROWSET can handle this, that is great.

BTW:

In Excel I'm using table-valued functions and do not specify "Table"...

I agree, the code for using OPENROWSET is very interesting.

But since the stored procedure has to return a result set, what is the advantage over using a table-valued function?