TP = "Bemerkungen"  '<--- Übergabewert
 
For Each tp1 As TabPage In tcAlleZusatzdaten.TabPages
  For Each c As Control In tp1.Controls
    If TypeOf c Is TabControl Then
      Dim tc As TabControl = DirectCast(c, TabControl)
      For Each tp2 As TabPage In tc.TabPages
        If tp2.Text.ToString = TP Then
          tc.SelectedTab = tp2
          ...
          ...
          Exit For
        End If
      Next
    End If
  Next
Next