extern HWND hDlgShow;//窗口句柄
HWND hReceieve = ::FindWindowEx(hDlgShow,0,"Edit",0);//取文本框句柄
CString strOld;
::GetWindowText(hReceieve,strOld.GetBuffer(2000),2000);
strOld.ReleaseBuffer();//必须释放缓冲
str.MakeUpper();//转换为大写
::SetWindowText(hReceieve,strOld + str);