The WinSetObjectData function is called to set data on a workplace object.

#define INCL_WINWORKPLACE
#include <os2.h>

HOBJECT    object;        /*  Handle to a workplace object. */
PSZ        pSetupString;  /*  Pointer to object-specific parameters. */
BOOL       rc;            /*  Success indicator. */

rc = WinSetObjectData(object, pSetupString);