Вместо procedure UcanCallbackFktEx (UcanHandle_p:byte; dwEvent_p: DWORD ;bChannel_p: BYTE; pArg_p: Tbyteptr); stdcall; external 'USBCAN32.dll';
написать
TUcanCallbackFktEx UcanCallbackFktEx (UcanHandle_p:byte; dwEvent_p: DWORD ;bChannel_p: BYTE; pArg_p: Tbyteptr); stdcall; external 'USBCAN32.dll';
?