First make sure that the listbox has RowSourceType set to "Table/Query". Then you would write the following code (adapted to your names) in the event procedure of the AfterUpdate event for th combo box:
Dim sSql As String
sSql = "SELECT " & cbxTableFields & " FROM Table ORDER BY " & cbxTableFields
Me.lbxTableContent.RowSource = sSql
Me.lbxTableContent.Requery
HTH
Felix Burkhard