-------------------------------------- MK Time Selection Follows Item Selection (Defer)-----------------------

local r = reaper

function Main()
local posx = pos
local endingx = ending
        local item = r.GetSelectedMediaItem(0, 0)
         if item ~= nil then  
            pos = r.GetMediaItemInfo_Value(item,"D_POSITION")
            ending = pos + r.GetMediaItemInfo_Value(item, "D_LENGTH")
            if (posx ~=  pos) or (endingx ~=  ending) then
                r.GetSet_LoopTimeRange(true, true, pos, ending, false)
            end
         end
         reaper.defer(Main)
end

Main()


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-- Set ToolBar Button ON
function SetButtonON()
  local is_new_value, filename, sec, cmd, mode, resolution, val = r.get_action_context()
  r.SetToggleCommandState( sec, cmd, 1 ) -- Set ON
  r.RefreshToolbar2( sec, cmd )
end

-- Set ToolBar Button OFF
function SetButtonOFF()
  local is_new_value, filename, sec, cmd, mode, resolution, val = r.get_action_context()
  r.SetToggleCommandState( sec, cmd, 0 ) -- Set OFF
  r.RefreshToolbar2( sec, cmd )
end
-----------------------------------------------------------------------------------
SetButtonON()


function OnExit()
SetButtonOFF()
end

r.atexit(OnExit)