need help with a script

[bluevayero]

hello. i want to make a script which talks to an npc and exchanges adena for gold bars. all is well until the moment it opens the window of the npc. there it cant exchange adena for gold bars

 

 

this is the window it opens. the BUYITEM(itemname[iD=],count) command doesnt work :S

ps: the shop has the same layout as a mammon shop