Make OnMouse functions ignore GameObjects that pass in front of them

Hello,

I am presently attempting to make OnMouseExit() ignore objects that pass in front of the object clicked on. I have a GameObject in the scene that will respond to being hovered over and clicked on (essentially, this object is the ground). I also have other GameObjects in the scene moving around (bullets). The ground object has a script on it that detects whether the mouse is currently interacting with it:

 public class MouseTarget : MonoBehaviour
 {
     private bool hovering;
     private bool mouseDown;
     
     void Start ()
     {
         this.hovering = false;
         this.mouseDown = false;
     }
     
     void Update ()
     {
         //Debug.Log (this.mouseDown);
     }
     
     void OnMouseEnter()
     {
         this.hovering = true;
     }
     
     void OnMouseExit()
     {
         this.hovering = false;
         this.mouseDown = false;
     }
     
     void OnMouseDown()
     {
         this.mouseDown = true;
         
     }
     
     void OnMouseUpAsButton()
     {
         this.mouseDown = false;
     }
     
     public bool Hovering{get{return this.hovering;}}
     public bool MouseDown{get{return this.mouseDown;}}
 }

The problem comes when one of the bullets passes beneath the mouse while it is currently clicked on the target. When that happens, OnMouseExit fires off, turning off mouseDown.

How do I prevent this behaviour? I want the mouse to essentially ignore the bullets.

Thank you for any assistance!

-J-