--------------------------------------------------------
    user_value = 40    -----  from 0 to 100 percent !
  --------------------------------------------------------
  function bla() end
  function nothing() reaper.defer(bla) end
  if not tonumber(user_value)
  or user_value < 0
  or user_value > 100
  then
    reaper.MB("Incorrect value at the beginning of the script", "Error", 0)
    nothing() return
  end
  local retval, tracknumber, itemnumber, fxnumber = reaper.GetFocusedFX2()
  if tracknumber == 0 then
    track = reaper.GetMasterTrack()
  else
    track = reaper.GetTrack(0,tracknumber-1)
  end
  if retval then
    reaper.Undo_BeginBlock()
    if retval == 1 then
      local wet_param = reaper.TrackFX_GetNumParams(track, fxnumber) - 2
      reaper.TrackFX_SetParam( track, fxnumber, wet_param , user_value/100 )
    elseif retval == 2 then
      local item = reaper.GetTrackMediaItem(track, itemnumber)
      local take = reaper.GetActiveTake(item)
      local wet_param = reaper.TakeFX_GetNumParams(take, fxnumber) - 2
      reaper.TakeFX_SetParam( take, fxnumber, wet_param, user_value/100 )
    end
    reaper.Undo_EndBlock('Set Dry/Wet parameter for focused FX by X value', -1)
  end