I tried to make the script as easy as possibly to modify for your needs.
#NoEnv ; Recommended for performance and compatibility with future AutoHotkey releases. #Persistent #SingleInstance Force CheckFor = Registrations are not open yet today. CheckHere = http://www.example.com/path/register.php SaveHere = E:\Source.txt SaveTemp = E:\Test.txt DisplayMessage = Registrations are open!`nGo Register now! ElseMessage = Registrations are currently closed. Contained = 0 ;Set to 0 if you want the messagebox to appear when CheckFor is absent. Set this to 1 if you want the messagebox when the sentence in "CheckFor" is present. Set to 2 if you want the message to appear when CheckFor is present and ElseMessage to appear when not present. Settimer, Check, 1800000 Check: { UrlDownloadToFile, %CheckHere%, %SaveHere% FileRead, V, %SaveHere% Loop, parse, V, `n, `r { If InStr(A_LoopField, CheckFor) { FileAppend, 1, %SaveTemp% } } FileRead, Status, %SaveTemp% If (Contained = "0") { If (Status = "1") {} Else MsgBox, %DisplayMessage% } Else If (Contained = "1") { If (Status = "1") { MsgBox, %DisplayMessage% } } Else If (Contained = "2") { If (Status = "1") { MsgBox, %ElseMessage% } Else MsgBox, %DisplayMessage% } FileDelete, %SaveTemp% FileDelete, %SaveHere% } return