As always i would like to answer my own question!
If you want to monitoring your NXT robot's results or if you want to adjust parameters same time you have to use bluetooth connection.
-First go Tools/Run on Target Hardware/Options
and choose comminication via bluetooth then set external mode on.
-Secondly you have to set host COM port manually
Then you have to go your bluetooth properties and go COM communication tab, check which port NXT using 1,2,3, etc.
-Finally you need to enter your COM port number.
Now you can use external mode without any problem.
Hope this helps.