mfc 钩子函数 error LNK2001

我在做一个查看星号密码的MFC程序（用的是局部钩子），在.h文件中定义了
private:
static HHOOK m_hkPass;
static BOOL m_bFinding;
protected:
static LRESULT CALLBACK PassObtainProc(int nCode,WPARAM wParam,LPARAM lParam);

链接的时候出现了如下错误：
Linking...
PassObtainDlg.obj : error LNK2001: unresolved external symbol "private: static struct HHOOK__ * CPassObtainDlg::m_hkPass" (?m_hkPass@CPassObtainDlg@@0PAUHHOOK__@@A)
PassObtainDlg.obj : error LNK2001: unresolved external symbol "private: static int CPassObtainDlg::m_bFinding" (?m_bFinding@CPassObtainDlg@@0HA)
Debug/PassObtain.exe : fatal error LNK1120: 2 unresolved externals

这两个变量只在void CPassObtainDlg::OnLButtonDown(UINT nFlags, CPoint point) ，void CPassObtainDlg::OnLButtonUp(UINT nFlags, CPoint point) 以及CallNextHookEx(m_hkPass,nCode,wParam,lParam);中用到了


请问是什么原因呢？是因为没有加头文件吗？使用钩子函数需要什么头文件呢？