develop UDF in Xll, Automation Add-in or VSTO
 

In my new project i have to create a user defined function that accesses a
SQL SERVER, execute a procedure and return the result. Also to perform that
task must be logged. This function must be available in any document.
I created an Automation Add-in with a UDF. This UDF call a VSTO that
checks if the user is logged in, but it shows a loginform , connected to SQL,
execute procedure and returns the result.
but I am unable to help and add description to the function and its variables.
How can i do?.
Is there a way to design all the requeriments in a single project?
I read that with Xll i can add descripction to my functions, but can i run
sql queries with xll?