filename = c:\log.txt
lines := 5
GUI, Add, Text, ReadOnly vMyTime, %A_Hour%:%A_Min%:%A_Sec%
GUI, Color, FFFFFF
GUI, Add, Text, vMyText w640 R%lines%, %Content%
GUI, Show

FileGetSize, oldsize, %filename%
newsize := 0
Loop, read, %filename%
{
   newsize += StrLen(A_LoopReadLine)+2 ; ANSI + `r`n
   Content .= A_LoopReadLine . "`n"
   Content := SubStr(Content, InStr(Content, "`n",0,-1, lines)+1)
   if (oldsize = newsize)
   {
   GuiControl, , MyTime, %A_Hour%:%A_Min%:%A_Sec%
   GuiControl, , MyText, %Content%
   GUI, Color,   FFFF99
   Sleep, 600
   GUI, Color,   FFFFFF
   }
   while oldsize = newsize
   {
      sleep 1000
      FileGetSize, oldsize, %filename%
   }

}

GuiClose:
Gui, Destroy
if !oldsize
   MsgBox Ошибка чтения, или файл "%filename%" не найден!
ExitApp