i would suggest the following (although it might not be exactly what you are looking for).....
add a tooltip to the form...
then (and this may be where my idea is different from what you want)
in add the following line to the selectedIndexChanged for the listbox
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Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
ToolTip1.SetToolTip(Me.ListBox1, ListBox1.SelectedItem)
End Sub
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So this will change the tooltip to the full text for the selected record