You need to create the SELECT.H include file for the Select library. This file contains the definitions for the constants used in the functions, as well as function definitions. The include file should look like this:
#define SL_BOX 1 /* Draw a solid border around the rectangle */
#define SL_BLOCK 2 /* Draw a solid rectangle */
#define SL_EXTEND 256 /* Extend the current pattern */
#define SL_TYPE 0x00FF /* Mask out everything but the type flags */
#define SL_SPECIAL 0xFF00 /* Mask out everything but the special flags */
int FAR PASCAL StartSelection(HWND, POINT, LPRECT, int);
int FAR PASCAL UpdateSelection(HWND, POINT, LPRECT, int);
int FAR PASCAL EndSelection(POINT, LPRECT);
int FAR PASCAL ClearSelection(HWND, LPRECT, int);
You should also use the include file in applications that use the selection functions. This will ensure that proper parameter and return types are used with the functions.