How to control the splitter line moving region using csplitterwnd class?

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C++

MFC

I have used the CSplitterWnd class to create a single-document-multiview program.Firstly,using CreateStatic() function splitted the window into three rows and one column.Then secondly,splitting the second row and the third row into two columns respectively.In the first step,using the CSplitterWnd class.In the second step,using the derived class from CSplitterWnd class.

When I ran the program,there had some splitter lines among the window.So my question is how to control the moving region of these splitter lines?In other words,how to control the top and bottom moving region for horizontal splitter lines,how to control the left and right moving region for vertical splitter lines?

What I have tried:

I overloaded three functions of CSplitterWnd class,OnLButtonDown(),OnMouseMove(),OnSetCursor() to deal with the messages.But there had no effort.So I was confused about these messages.