cross-sell

Hi there,
I am trying to add cross sell and up sells columns this way
_crosssell_ids
meta value
Edit formater: media set (?)
But something goes wrong, I received an error message in front end.
I tried to use edit formater simple and to edit the id; I see all my cross sell id for my products but if I try to edit a new ID it doesn't work

Nothing, It doesn't work

if I try to edit that field my data disappear after two seconds

Have a look to my added Image. If I edit the cross-sell by the traditional way, then I can read the right ID in the excel like pm; but if I try to edit it, it doen't work

Sorry but It doesn't work yet

I am sorry but It doesn't work. Have a look here, if I edit that field I can't find my IDs in the "traditional" view; still nothing change in front-send