Rotate an object around another on input

I have a camera placement GO. My camera locks onto t$$anonymous$$s position and looks at the target.

In OnGUI i have 4 buttons to alter the camera placements orientation(Screen: top center, bottom center, left center, right center), the top and bottom buttons are for zooming in and out. The buttons on the left and right are for rotating around center of the target. My top and bottom buttons work fine, but i am stumped on the rotate around portion for the left and right buttons.

 function OnGUI()
 {
     if(GUI.RepeatButton(guiRects[0],guiButton))
     {
         transform.RotateAround (target.transform.position,target.transform.up,Time.deltaTime);
     }
     if(GUI.RepeatButton(guiRects[1],guiButton))
     {
         transform.RotateAround (target.transform.position,target.transform.up,-Time.deltaTime);
     }
     if(GUI.RepeatButton(guiRects[2],guiButton))
     {
         camModY-=Time.deltaTime;
         camModX-=Time.deltaTime;
     }
     if(GUI.RepeatButton(guiRects[3],guiButton))
     {
         camModX+=Time.deltaTime;
         camModY+=Time.deltaTime;
     }
 }

 function Update () 
 {    
     if(mainCamera.transform.position!=camPosition)
     {
         camPosition=Vector3(target.transform.position.x+camModX,target.transform.position.y+camModY,target.transform.position.z+camModX);
         mainCamera.transform.position=camPosition;
     }
     mainCamera.transform.LookAt(target);
 }

I need to rotate the camera position around the target object in the repeat button. Im pretty sure im close, just need a little help.

Thanks in advance.