local hwnd = win.handle("c=TTOTAL_CMD")
local i, From, To, Result, Unmark
local Step = 2
local What = "All"
local Panel = ifelse(tc.active(hwnd) == "left", 8, 7)
local TMLB = childwin.handle(hwnd, "TMyListBox", Panel)
local Current = win.sendmessage(TMLB, 0x0188, 0, 0)
local Counter = win.sendmessage(TMLB, 0x018B, 0, 0)
local Cap = "File " ++ Current ++ " of " ++ Counter

Result = Inputdialog("~Step=Step, What=Files to mark??All|Current & above|Current & below, Unmark=Unmark??", Cap)

if(Result == 0)
	quit

if(miscplugin.is_int(Step) != "1" || Step <= 0) do
	messagebox("ok error", "Invalid step: " ++ Step, "'MarkStep' Script")
	quit
endif

if(What == "All") do
	From = 0
	To = Counter
elseif(What == "Current & above")
	From = 0
	To = Current
elseif(What == "Current & below")
	From = Current
	To = Counter
endif

Unmark = not(Unmark)

for(i = From; i < To; i = i + Step)
	win.sendmessage(TMLB, 0x0185, Unmark, i)
endfor

win.setfocus(hwnd)