Uncheck ListBox Selections

I have a form with 3 checkboxes. When any of the 3 checkboxes are checked, a set number of items are selected from a listbox. If a checkbox is checked, and then a new checkbox is checked, the listbox selection is cleared and selected with the new values from the new checkbox.

Problem: How can I code this so that if I check a checkbox and then deselect that same checkbox, my selected listbox items are cleared? Only when I select a different checkbox are they then cleared and repopulated.

Private Sub CheckBox1_Exit(ByVal Cancel As MSForms.ReturnBoolean)
Dim lngitem As Long
For lngitem = 0 To ListBox1.ListCount - 1
ListBox1.Selected(lngitem) = False
Next
CheckBox1.Value = False
End Sub..............................