GUI Popup won't work in conjunction with mouseOver AND Mouse Click ?

I have a GUI Texture popup that is supposed to work when the player does a mouseOver on a certain object and clicks the mouse button.

It works fine as just a simple popup on mouseOver BUT... I only want the popup to happen when the player/cursor hovers over the object AND clicks the mouse button

Code (JavaScript):

1. #pragma strict
2.  
3. private var pressedButton : boolean = false;
4. public var Clue01GUI: Texture;
5.  
6. function OnMouseOver()
7. {
8.     pressedButton = true;
9. }
10.  
11. function OnMouseExit()
12. {
13.     pressedButton = false;
14. }
15.  
16. function OnGUI()
17. {
18.     if(pressedButton == true)
19.     {
20.         GUI.DrawTexture(Rect(350,95,300,410), Clue01GUI);
21.     }
22. }

Any ideas guys?