>The most common cause of this is error is the case used in declaration not
matching that in the DLL.

Could be, too, that he's not exporting the functions in a way that avoid the compiler mangling, er sorry, decorating the names.

Anyway, if that's the case, just add a .DEF file to the project and use the EXPORTS statement:

LIBRARY BTREE
DESCRIPTION "Implements a binary tree."
EXPORTS
Insert @1
Delete @2
Member @3
Min @4