Maybe this helps:

int pos1,pos2;
m_editControl->GetSel(pos1,pos2); /// this returns the position of the caret in characters
// After this you can get the string with GetWindowText
// i used it to simulate Ctrl+Enter when Enter only was pressed.
CString t;
m_editControl->GetWindowText(t);
t.Insert(pos1,'\r');
t.Insert(pos1+1,'\n');
m_editControl->SetWindowText(t);
m_editControl->SetSel( pos1+2,pos1+2,FALSE); // set the caret after the two new characters \r and \n

I hope this helps.

(sorry for my english)

bye.