Check if clicked in active word document instead main Word Window

I use Word automation in my VB6 application

-I want to check if the user mouseclicks in the actual document area of the active Word window. So far I can check with a DLL if the user clicks on the main Word Window (including the menu, and proppopupwindows, and i want to avoid this)

So i have a DLL that fires my VB CallBack function when a general click (can be on any external app) happens.

VB Code:

public function CallBack(...) 'fires when a general mouseclick happens
  ' I have made a function to check  which is the active window, and gets the handle
  Dim ClassName as string
  'This function contains a GetClassName API
  ClassName = NameActiveWindow(Hendel)
 if ClassName <> "OpusApp" then
   'We are not in a Word App so exit
   exit function
 end if
 
 '-Do some  actions
 ...
end function

So i want to expand the above function, especially the ClassName test