function find(str, key) {
  p = pos(str, key);
  if (p == 0) {
    return false;
  }
  return (pos(mid(str, p + len(key)), key) > 0);
}

key = InputBox("検索する文字列を入力してください。");
if (key == "") {
  return;
}

SB = SelBottom;
ST = SelTop;
SL = SelLeft;
SR = SelRight;

for (y = SB; y >= ST; y--) {
  found = false;
  for (x = SL; x <= SR && !found; x++) {
    if (find([x,y], key)) {
      found = true;
    }
  }
  if (!found) {
    DeleteRow(y);
  }
}