jQuery Grid Plugin - jqGrid

hello, i try to add extra  data to post grid (in del action),

i try use

delData: {cmd: function() {return 'gruppo';}} but nothing uppen,

i try use:

beforeSubmit: function(postdata, formid){postdata.cmd='gruppo';  return[true];} nothin uppen,

strange thing is that with add button io use

beforeSubmit: function(postdata, formid){postdata.cmd='gruppo';  return[true];} and it's goes

can someone hjelp me please?

thank's