How to convert this buttons into combo box

hi

I need to convert these buttons into combo box and these buttons are used to disable and enable game objects and i want to do that thing using combo box. it possible to make it combo box. if it is possible how can i do it. please answer me.

this is the code that i have written

16295-kk.jpg
function OnGUI (){

GUI.Box(Rect(1500,10,500,500),“Tools”);

if (GUI.Button (Rect (1720,40,200,50), "Wall Main Door")) {
  target.SetActive(true);
}

if (GUI.Button (Rect (1500,40,200,50), "Wall main door Delete")) {
  target.SetActive(false);
}

if (GUI.Button (Rect (1500,100,200,50), “Wall main window Delete”)) {
wall_window_main.SetActive(false);
}
if (GUI.Button (Rect (1720,100,200,50), “Wall main window”)) {
wall_window_main.SetActive(true);
}

if (GUI.Button (Rect (1720,160,200,50), "roof")) {
  roof.SetActive(true);
}

if (GUI.Button (Rect (1500,160,200,50), "roof delete")) {
  roof.SetActive(false);
}

 if (GUI.Button (Rect (1500,220,200,50), "Tower Delete")) {
  wall_toi.SetActive(false);
}

 if (GUI.Button (Rect (1720,220,200,50), "Tower")) {
  wall_toi.SetActive(true);
}

regards
budd

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