On Nov 19, 2009, at 9:55 AM, Max Taylor wrote: > Any reference to or anything that needs to know about those > structures causes an error. What error? Is it an "Implicit declaration" error? If yes, see below. If not, please post. > Any reference to MxClassDR, defined in the C file, is not seen. This sounds like the same issue Robert P. addressed in his November 5th response. Because each C file is a separate compilation unit, it will need an include of the header file ( .h ) with the declarations of the functions the code is calling. Any C file that needs access to the function(s) will also need the include of the header file. btw: how did you end up going down this path of needing to manipulate the C files? Is it not possible to do everything within FB? I confess I didn't read all your previous posts, so you've probably answered that already. Brian S