How to assign a different tooltip to each GUI button？

In Unity's GUI Basic Guide, the follow code shows how to assign a tooltip to a button:

     // This line feeds "This is the tooltip" into GUI.tooltip
     GUI.Button (Rect (10,10,100,20), GUIContent ("Click me", "This is the tooltip"));
     // This line reads and displays the contents of GUI.tooltip
     GUI.Label (Rect (10,40,100,20), GUI.tooltip);

Now I want to assign two different tooltips to two buttons. I did that like this:

     GUI.Button(new Rect(10, 10, 100, 20), new GUIContent("Click me", "This is the tooltip"));
     
     GUI.Label(new Rect(10, 40, 100, 20), GUI.tooltip);

     GUI.Button(new Rect(150, 10, 100, 20), new GUIContent("Click Another", "This is another tooltip"));
     
     GUI.Label(new Rect(150, 40, 100, 20), GUI.tooltip);

When the mouse hovered over the first button, I got both "This is the tooltip" and "This is another". How to assign the second tooltip "This is another tooltip" to the second button? Thank you!