[Closed] Mapbutton rightclick ，Does not take effect in 3ds max 2018

I tried many times，mapbutton rightclick ，Does not take effect in 3ds max 2018。
It displays the system’s built-in menus when right-clicked in 2018, instead of custom events, but in MAX2013 it is a normal display of custom events.
I don’t know why this is happening. Does anyone know how to solve it?

My English is not good, please don’t mind

rollout test_mapbutton "Background"
(
  label sbm_lbl "Background Map:"
  mapbutton choosemap "<<none>>" tooltip:"Select Background Map" width:120
  on choosemap picked texmap do
  (
    environmentmap = texmap
    choosemap.text=classof texmap as string
  )
  on choosemap rightclick do messagebox "rightclick"

)
createDialog test_mapbutton

2018

2013