If you want to add an Input Box or any other command that will only show up on one tab its simple. All you need to do is place the code under the GUICtrlCreateTabItem for the tab you want it on. I added an Input Box on the URLs tab in the code below but I took out your list that was there becase two controls over lapping is not a good thing and I didn't know where you wanted it to show up so just add it back in where ever you need it.
CODE#include <GUIConstants.au3>
;=================================GUI=========================================
$Form1 = GUICreate("PoXee", 358, 444, 201, 125)
$menu = GUICtrlCreateMenu("&File")
$eMenu = GUICtrlCreateMenuitem("Exit",$menu)
$hMenu = GUICtrlCreateMenu("&Help")
$aMenu = GUICtrlCreateMenuitem("About", $hMenu)
$tab = GUICtrlCreateTab(0, 48, 100, 17)
GUICtrlSetFont(-1, 8, 400, 0, "Tahoma")
$progress = GUICtrlCreateProgress(0, 0, 353, 9)
GUICtrlSetData(-1, 25)
;$pList = GUICtrlCreateList("", 0, 64, 353, 357)
$pLabel = GUICtrlCreateLabel("", 0, 424, 187, 17)
GUICtrlSetFont(-1, 8, 400, 0, "Tahoma")
$nLabel = GUICtrlCreateLabel("", 192, 424, 163, 17)
GUICtrlSetFont(-1, 8, 400, 0, "Tahoma")
$save = GUICtrlCreateButton("Save", 296, 16, 57, 17, 0)
$exit = GUICtrlCreateButton("Exit", 296, 40, 57, 17, 0)
$load = GUICtrlCreateButton("Load", 216, 16, 57, 17, 0)
$clear = GUICtrlCreateButton("Clear", 216, 40, 57, 17, 0)
$leech = GUICtrlCreateButton("Leech", 144, 24, 57, 17, 0)
$tab1 = GUICtrlCreateTabItem("Leeched")
;add any code here you want and it will only show up on the Leeched tab
$tab2 = GUICtrlCreateTabItem("URLS")
$input = GUICtrlCreateInput("Text Here", 15, 100, 200, 17)
;add any code here and it will only show up on the URLs tab
GUICtrlCreateTabitem ("")
;==============================================================================
GUISetState(@sw_show)
While 1
$msg = GUIGetMsg()
Select
Case $msg = $GUI_EVENT_CLOSE
ExitLoop
Case $msg = $exit
ExitLoop
Case $msg = $tab
if guictrlread($tab) = 1 then WinSetTitle("URLS","","")
if guictrlread($tab) = 2 Then WinSetTitle("LEECHED", "","")
Case Else
;;;
EndSelect
WEnd