How to check whether a CString object contain surrogate character or not in c++?

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VC6

C++

Hi all,
In my visual c++ project, i want to check whether a CString object contain surrogate characters or not.
This is because i want to display a string on a button. But if string containg surrogate charectr whose length more than button length, then exceed charectrs are shown like small box( □ ). so that i want to check each charecter in the string is it hight surrogate charecter or low surrogate charecter. how it is perform?