field1,field2,field3,field4
a1,b1,"c1, some text, my text",d1
a2,b2,"c2, some text, my text",d2
a3,b3,"c3, some text, my text",d3
a4,b4,"c4, some text, my text",d4

dxMemData.Active:=False;
dxMemData.DelimiterChar:=',';
dxMemData.LoadFromTextFile('myfile.csv');
dxMemData.Active:=True;

field1,field2,field3,field4
a1,b1,"c1, some text, my text","d1, e1"
a2,b2,"c2, some text, my text",d2
a3,b3,"c3, some text, my text",d3
a4,b4,"c4, some text, my text",d4

var FileOnNet, LocalFileName: string;
sl : TStringList;
field : string;
i, AOffset, AQuoteL, AQuoteR: Integer;
begin
...
sl := TStringList.Create;
sl.LoadFromFile('myfile.csv');

  for i := 0 to sl.Count - 1 do
  begin
  AOffset := 0;
  sl[i] := StringReplace(sl[i], ',', #9,[rfReplaceAll]);
    repeat

    AQuoteL := PosEx('"', sl[i], AOffset+1);
    AQuoteR := PosEx('"', sl[i], AQuoteL+1);
    if AQuoteL > 0 then
    begin
    field := Copy(sl[i], AQuoteL+1, AQuoteR-AQuoteL-1);
    field := StringReplace(field, #9, ',',[rfReplaceAll]);
    sl[i] := StuffString(sl[i], AQuoteL+1, AQuoteR-AQuoteL-1, field);

    AOffset := AQuoteR + 1;
    end

    until PosEx('"', sl[i], AOffset+1) = 0;

  end;

sl.SaveToFile('myfile1.csv');
    dxMemData2.Active:=False;
    dxMemData2.DelimiterChar:=#9;
    dxMemData2.LoadFromTextFile('myfile1.csv');
    dxMemData2.Active:=True;
sl.Free;
end;