Here's the OK button handler from a dialog app I wrote a while ago that updates the created/accessed/modified times for a given file (error checking removed):
Code:
case ID_OK:
{
	// Get the name of the file...
	TCHAR szFile[MAX_PATH] = {0};
	GetWindowText(GetDlgItem(hwnd, IDC_FILENAME), szFile, sizeof(szFile) / sizeof(TCHAR));

	// Get each of the date/time values...
	SYSTEMTIME st = {0};
	st.wMonth  = GetDlgItemInt(hwnd, IDC_MONTH, NULL, FALSE);
	st.wDay    = GetDlgItemInt(hwnd, IDC_DAY,   NULL, FALSE);
	st.wYear   = GetDlgItemInt(hwnd, IDC_YEAR,  NULL, FALSE);
	st.wHour   = GetDlgItemInt(hwnd, IDC_HOUR,  NULL, FALSE);
	st.wMinute = GetDlgItemInt(hwnd, IDC_MIN,   NULL, FALSE);

	// Convert the SYSTEMTIME to a FILETIME...
	FILETIME ft = {0};
	SystemTimeToFileTime(&st, &ft);

	// Write the new filetime...
	HANDLE hFile = CreateFile(szFile, FILE_WRITE_ATTRIBUTES, NULL, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
	SetFileTime(hFile, &ft, &ft, &ft);
	CloseHandle(hFile);

	return FALSE;
}