If you wish to make a script in your item that interacts with GHI, then you can see the functions avaliable here.

General

GHI_Message(msg)
GHI_ReloadUI()
GHI_ColorString(s,r,g,b)
GHI_PrintArray(tableName or table)

Actionbar

GHI_GetActionBarData(bar,slot)
GHI_SetActionBarData(bar,slot,id)
GHI_ShowAllActionbars()
GHI_HideUnusedActionbars()

Book

GHI_BookNextPage()
GHI_BookPrevPage()
GHI_ShowBook(title,text,edit,material,font,N,H1,H2)
GHI_TranscribeTextItem()
GHI_TranscribeMailboxLetter()

Buff

ApplyGHIBuff(name,text,texture,untilCancelled,filter,debuffType,duration,cancelable,stackable,count,delay)
RemoveGHIBuff(name,count)
RemoveAllGHIBuffs()
CountGHIBuff(name,unit)

Communication

GHI_SendLink(name,player)
GHI_SendAreaEffect(typed,...)
GHI_SendItemData(ID,player)
GHI_SendPing(player)

Container

GHI_GetContainerInfo(container,slot)
GHI_GetNumContainers(filter)
GHI_GetContainerList(filter)
GHI_GetContainerSize(num)
GHI_GetSlotList(container)
GHI_ToggleBackpack()
GHI_updateContainerFrameAnchors()
GHI_UpdateContainers()
GHI_NextMainBagPage()
GHI_PrevMainBagPage()
GHI_SelectSecBag(num,id)
GHI_MaintainMainBags()
GHI_IsBagEmpty(id)
GHI_GetBagID(id)
GHI_GetFreeSpace()
GHI_FindItem(ID,all)
GHI_CountItem(ID)
GHI_ProduceItem(ID,amount,ToGHP)
GHI_InsertItem(ID,amount,ToGHP)

Createitem

GHI_CreateItem(name,icon,quality,white1,white2,comment,amount,stackSize,copyable,rightClick,rightClicktext,editID,
   duration,durationWhenTrade,durationRealTime,editable,changeStack)
GHI_GetItemInfo(ID,returnTable)
GHI_GetRightClickInfo(ID)
GHI_IsOfficialItem(ID)
GHI_GetVersions(ID)
GHI_IsCopyable(ID)
GHI_IsEditable(ID)
GHI_ClearItemCatche()
GHI_GenerateID()
GHI_ExportItem(ID,amount,scriptBefore,req,scriptAfter)
GHI_ImportItem(code)

Cursor

GHI_SetCursor(Type,details)
GHI_ResetCursor()
GHI_GetCursor()
GHI_GetCursorPreDetails(Type)
GHI_AddExternalPreDetails(Type,details)

Display

GHI_SetCustomSlotInfo(slotRef,info)
GHI_GetPlayerEquipmentDisplay()
GHI_ShowPlayerEquipmentDisplay()
GHI_SetTargetEqDisplay(unit)
GHI_CopyTargetEqDisplay()
GHI_ToggleTargetEqDisplay()

Links

GHI_GenerateLink(ItemID)

Useitem

GHI_UseItem(bag,slot)
GHI_GetCurrentItem()
GHI_DoEmote(data,waitTime,ID)
GHI_DoSay(data,waitTime,ID)
GHI_IsStdEmote(command)
GHI_DoScript(data,waitTime)
GHI_GetItemUseInfo(ID,index)
GHI_CheckReq(Type,text)