Remove duplicates in a list

Here's the code:

Sub remove_dupe_list(lst As ListBox)
For a = 0 To (lst.ListCount - 1)
 X$ = LCase(lst.List(a))
 For b = 0 To (lst.ListCount - 1)
 Y$ = LCase(lst.List(b))
  If a <> b And X$ Like Y$ Then lst.RemoveItem b
 Next b
Next a

End Sub

But when I use it, my program freezes. Anyone have a better code or can fix it?