window border width and height in Win32 - how do I get it?

void ClientResize(HWND hWnd, int nWidth, int nHeight)
{
  RECT rcClient, rcWind;
  POINT ptDiff;
  GetClientRect(hWnd, &rcClient);
  GetWindowRect(hWnd, &rcWind);
  ptDiff.x = (rcWind.right - rcWind.left) - rcClient.right;
  ptDiff.y = (rcWind.bottom - rcWind.top) - rcClient.bottom;
  MoveWindow(hWnd,rcWind.left, rcWind.top, nWidth + ptDiff.x, nHeight + ptDiff.y, TRUE);
}

void ClientResize(HWND hWnd, int nWidth, int nHeight)
{
  RECT rcClient, rcWind;
  POINT ptDiff;
  GetClientRect(hWnd, &rcClient);
  GetWindowRect(hWnd, &rcWind);
  ptDiff.x = (rcWind.right - rcWind.left) - rcClient.right;
  ptDiff.y = (rcWind.bottom - rcWind.top) - rcClient.bottom;
  MoveWindow(hWnd,rcWind.left, rcWind.top, nWidth + ptDiff.x, nHeight + ptDiff.y, TRUE);
}

void ClientResize(HWND hWnd, int nWidth, int nHeight)
{
  RECT rcClient, rcWind;
  POINT ptDiff;
  GetClientRect(hWnd, &rcClient);
  GetWindowRect(hWnd, &rcWind);
  ptDiff.x = (rcWind.right - rcWind.left) - rcClient.right;
  ptDiff.y = (rcWind.bottom - rcWind.top) - rcClient.bottom;
  MoveWindow(hWnd,rcWind.left, rcWind.top, nWidth + ptDiff.x, nHeight + ptDiff.y, TRUE);
}

int border_thickness = GetSystemMetrics(SM_CXSIZEFRAME);

GetClientRect(hWnd, &rcClient);
GetWindowRect(hWnd, &rcWind);
int border_thickness = ((rcWind.right - rcWind.left) - rcClient.right)/2;