function plugindef()
   -- This function and the 'finaleplugin' namespace
   -- are both reserved for the plug-in definition.
   finaleplugin.Author = "Jari Williamsson"
   finaleplugin.CategoryTags = "Layout, Page, System, UI"
   return "Locked Systems Per Page", "Locked Systems Per Page",
           "Creates a predefined number of systems per page (by inserting page breaks)."
end

-- Show user dialog box
local dialog = finenv.UserValueInput()
dialog.Title = "Systems Per Page"
dialog:SetTypes("Number", "Number", "Number")
dialog:SetDescriptions("Number of systems per page:", "Start at page:", "Do it for max no of pages:")
dialog:SetInitValues(6, 1, 999)
local returnvalues = dialog:Execute()
if not returnvalues then return end

local systemsperpage = returnvalues[1]
local currentprocesspage = returnvalues[2]
local maxnoofprocesspages = returnvalues[3]

if (systemsperpage < 1) then
    print ("Input error: Invalid number of systems per page.")
    return 
end

if currentprocesspage < 1 then
    print ("Input error: Invalid start page number.")
    return 
end

local pages = finale.FCPages()
local pageprocesscounter = 0

while true do    
    -- Reload the page layout every time, since the layout contents changes
    finale.FCStaffSystems.UpdateFullLayout()
    if pageprocesscounter > maxnoofprocesspages then break end
    pages:LoadAll()
    if pages.Count < currentprocesspage  then break end

    -- Create the local-scope variables before any goto:s
    local system = finale.FCStaffSystem()
    local measure = finale.FCMeasure()    

    -- Get the page layout to process
    page = pages:GetItemAt(currentprocesspage - 1)
    local firstsysnumber = page:GetFirstSystem()
    local lastsysnumber = page:CalcLastSystem()
    
    -- Skip pages with no system layout, such as empty pages    
    if firstsysnumber < 1 then goto continue end    
    if lastsysnumber < 1 then goto continue end

    -- Check if the page contains enough systems to split the contents
    if  (lastsysnumber - firstsysnumber + 1) < systemsperpage then
        print ("Can't continue. Page", page:GetItemNo(), "contains less than", systemsperpage, "systems.")
        return
    end

    -- Load the system where the break should appear    
    system:Load(firstsysnumber + systemsperpage)
    if (system.FirstMeasure < 1) then goto continue end
    -- Change the measure attribute of the first measure to a page break    
    measure:Load(system.FirstMeasure)
    measure.PageBreak = true
    measure:Save()

    -- Process the next page
    :: continue ::
    currentprocesspage = currentprocesspage + 1
    pageprocesscounter = pageprocesscounter + 1    
end