Code:

{+------------------------------------------------------------

| Function FindTextBackwards

|

| Parameters :

|   findWhat: text to find

|   inString: string to find it in

|   startAt : character index to start at (1-based)

|   caseSensitive: determines whether search is case-sensitive

|   words   : if true the characters immediately surrounding

|             a found location must not be alphanumeric

| Returns    :

|   character index (1-based) of first character of a found

|   location, or 0, if the text was not found.

| Description:

|   Performs a simple sequential search for a string in a larger

|   string, starting at the specified position and working towards

|   the start of the string.

| Error Conditions: none

| Created: 27.02.99 by P. Below

+------------------------------------------------------------}

function FindTextBackwards(findWhat, inString : string;

  startAt : integer;

  caseSensitive, words : boolean): integer;

var

  i, patternlen, findpos : integer;

  lastchar, firstchar : char;

begin

  Result := 0;  { assume failure }

  patternlen := Length(findWhat);

  { Do a few sanity checks on the parameters }

  if (patternlen = 0) or

    (startAt < patternlen) or

    (Length(inString) < patternlen) then

    Exit;

  if not caseSensitive then

   begin

    { convert both strings to lower case }

    findWhat := AnsiLowercase(findWhat);

    inString := AnsiLowercase(inString);

  end; { If }

  i := startAt;

  lastchar := findWhat[patternlen];

  firstchar := findWhat[1];

  while (Result = 0) and (i >= patternlen) do

   begin

    if inString[i] = lastchar then

     begin

      findPos := i - patternlen + 1;

      if inString[findPos] = firstchar then

       begin

        { We have a candidate. Compare the substring of length

         patternlen starting at findPos with findWhat. With

         AnsiStrLComp we can do that without having to copy

         the substring to a temp string first. }

        if AnsiStrLComp(@findWhat[1], @inString[findPos],

          patternlen) = 0 then

         begin

          { We have a match! }

          Result := findPos;

          if words then

           begin

            { Check the characters surrounding the hit. For the hit

             to constitute a word they must not be alphanumeric. }

            if (findPos > 1) and

              IsCharAlphanumeric(inString[findPos - 1]) then

             begin

              { Not a match after all, <sigh>. }

              Result := 0;

            end { If }

            else

             begin

              if (i < Length(inString)) and

                IsCharAlphanumeric(inString[i + 1]) then

               begin

                { Not a match after all, <sigh>. }

                Result := 0;

              end; { If }

            end; { Else }

          end; { If }

        end; { If }

      end; { If }

    end; { If }

    Dec(i);

  end; { While }

end; { FindTextBackwards }

procedure TForm1.Button1Click(Sender : TObject);

var

  findPos : integer;

begin

  findPos := FindTextBackwards(findEdit.Text,

    richedit1.Text,

    richedit1.selstart + 1,

    caseCheckbox.Checked,

    wordsCheckbox.Checked);

  if findPos > 0 then

   begin

    with richedit1 do

     begin

      selstart := findPos - 1;

      sellength := findEdit.GetTextLen;

      Perform(em_scrollcaret, 0, 0);

      SetFocus;

    end;

  end

  else

    ShowMessage('Text not found');

end;