List Box won't refresh

[Don]

I am using Access 2007.

I have a form with 3 listboxes. When I click on the first listbox, the
second is populated with info related to the first list box. When I click in
the second listbox, the third listbox is populated with info related to the
second listbox.

Here is my problem. When I click in the first listbox, after the third
listbox has been populated, the second listbox requeries and is repopulated
appropriately; however, the third listbox does nothing.

I believe I know why this is happening, but I don't know enough to work
through it.
I've concluded that the third listbox is still tied to the last selection I
made in the second listbox.

How can I get the third listbox to show no values when I click on the first
listbox? Thanks in advance.

 

[NEWER USER]

In the Properties box - On Got Focus of the FIRST list box, type
Me!"Name of ThirdList Box".RowSource = ""

No quotes around the name of list box.

 

[Don]

This works to empty the third listbox; however, when I select a new value in
the first listbox and then click a value in the second listbox, the third
listbox remains blank. Any thoughts?