VBA Calling C++

Create a new project
language - C++, platform - Windows, project - Library
Dynamic Link Library (DLL)

delete all the source files
delete all the header files

Project Properties
change your drop-downs to "ALL" for both

Configuration Properties > General
check - C++ Langauge Standard = Default (ISO C++ 14 Standard)

Configuration Properties > Debugging
check - Command = C:\Program Files\Microsoft Office\root\Office16\EXCEL.EXE

Configuration Properties > C/C++ > All Options
check Precompiled Header = Not Using Precompiled Headers
check Precompiled Header File = blank

Configuration Properties > Linker > All Options
check - Module Definition File = blank

GetTime.cpp

Add a source file.

#include <windows.h> 
#include <time.h> 

#define SECS_PER_DAY (24 * 60 * 60) 

long current_system_time(void) 
{ 
   time_t time_t_T; 
   time(&time_t_T); 

   struct tm tm_T; 

   time_t time_t_T2 = time(0); 

   localtime_s(&tm_T, &time_t_T2); 

   return tm_T.tm_sec + 60 * (tm_T.tm_min + 60 * tm_T.tm_hour); 
} 

double __stdcall get_system_time_C(long trigger) 
{ 
   return current_system_time() / (double)SECS_PER_DAY; 
} 

Build the project

SS

GetTime.def

Add a definition file.
Project > Add > New Item
under Visual C++, select "Code"
SS
Select "Module Definition File"

LIBRARY 
EXPORTS 
   get_system_time_C 

The module definition file must be explicitly added to the project settings
Configuration Properties > Linker > Input
Module Definition File = GetTime.def

Build the project

SS

check and change the "Solution Platform" drop-down to x64
SS

Create the Workbook

Save the file as GetTime.xlsm
Open the VBA Editor and add a code module

Declare PtrSafe Function get_system_time_C Lib _ 
   "C:\Users\*username"\source\repos\exceldll\x64\Debug\exceldll.dll" _ 
   (ByVal trigger As Long) As Double 
   
Public Function Get_C_System_Time(trigger As Double) As Double 
   Get_C_System_Time = get_system_time_C(0) 
End Function 

Public Function Get_VBA_Time(trigger As Double) As Double 
   Get_VBA_Time = Now 
End Function 

Enter the following information into cells "B1, B2, B3"

Start Debugging

SS

Open the excel file
press F9