Help with sorting a rich text box - and then outputting results to another rich text box

Hello, I have a rich text box, and want to filter the contents of this rich text box into another rich text box. Initially, the contents of the first rich text box are loaded by the file reader of openfiledialog. This means they are in memory. How do I go about sorting and filtering the content? Basically, my first rich text box has a loaded file consiting of: MODEL 1 ATOM 1 N GLY A 1 296.995 21.768 -6.913 1.00 0.00 N ATOM 2 CA GLY A 1 296.814 21.433 -8.356 1.00 0.00 C ATOM 3 C GLY A 1 295.982 20.178 -8.579 1.00 0.00 C ATOM 4 O GLY A 1 295.381 19.654 -7.643 1.00 0.00 O ATOM 5 HA2 GLY A 1 296.321 22.263 -8.844 1.00 0.00 H ATOM 6 HA3 GLY A 1 297.784 21.294 -8.810 1.00 0.00 H ATOM 7 H1 GLY A 1 297.491 22.677 -6.814 1.00 0.00 H ATOM 8 H2 GLY A 1 297.556 21.035 -6.439 1.00 0.00 H ATOM 9 H3 GLY A 1 296.072 21.842 -6.444 1.00 0.00 H ATOM 10 N PRO A 2 295.945 19.670 -9.815 1.00 0.00 N ATOM 11 CA PRO A 2 295.156 18.482 -10.172 1.00 0.00 C ATOM 12 C PRO A 2 295.508 17.239 -9.360 1.00 0.00 C etc... And I need to sort and filter so that the output looks like this: >Chain_A 1 - GLY PRO ASN THR GLU PHE ALA LEU SER LEU LEU ARG LYS ASN ILE MET THR ILE THR THR SER LYS GLY GLU PHE THR GLY LEU GLY ILE HIS ASP ARG VAL CYS VAL ILE PRO THR HIS ALA GLN PRO GLY ASP ASP VAL LEU VAL ASN 51 - GLY GLN LYS ILE ARG VAL LYS ASP LYS TYR LYS LEU VAL ASP PRO GLU ASN ILE ASN LEU GLU LEU THR VAL LEU THR LEU ASP ARG ASN GLU LYS PHE ARG ASP ILE ARG GLY PHE ILE SER GLU ASP LEU GLU GLY VAL ASP ALA THR 101 - LEU VAL VAL HIS SER ASN ASN PHE THR ASN THR ILE LEU GLU VAL GLY PRO VAL THR MET ALA GLY LEU ILE ASN LEU SER SER THR PRO THR ASN ARG MET ILE ARG TYR ASP TYR ALA THR LYS THR GLY GLN CYS GLY GLY VAL LEU 151 - CYS ALA THR GLY LYS ILE PHE GLY ILE HIS VAL GLY GLY ASN GLY ARG GLN GLY PHE SER ALA GLN LEU LYS LYS GLN TYR PHE VAL GLU LYS GLN >Chain_B 1 - LEU GLU ALA LEU PHE GLN Would this be able to be done from a rich text box, or is it best to use something else? Thank-you, Kind Regards, Timothy Johansen.