Is your question really about "header files"? VBA does not use header files
(that list all functions, their arguments, return types, etc.), because
this is just extra work for the programmer and can lead to errors. In C, if
a programmer changes the main code file, and forgets to change the header
file, then a compile error results.

In VBA, you open up the project that has the routines that you want to
inspect, then go into the Object Browser (<F2 key in the VBA Editor),
select the Library in the Library drop-down combo box, then inspect the
methods and properties, as mentioned in a previous post by Peter T.

--
Regards,
Bill Renaud