Call this function to get the position (top-left corner) of a given character within this CEdit object.
The character is specified by giving its zero-based index value. If nChar is greater than the index of the last character in this CEdit object, the return value specifies the coordinates of the character position just past the last character in this CEdit object.
This member function is available beginning with Windows 95 and Windows NT 4.0.
For more information, see EM_POSFROMCHAR in the Windows SDK.