Your mail is here

First bit of your code is inefficient. Its better to convert the input into lower case then you don't have to worry about users typing in capitals.

Also, your Command() function is calling itself if the user types anything other than "notify". Using recursion like that is setting you up for a stack overflow.

Repeat
  Command$=Lower(Input$("/cmd>"))
  Parse(Command$)
Forever

Function Parse(txt$)
  Select txt$
    Case "notify"
      cmd=1
    Default
      RuntimeError("Command not recognised")
  End Select
End Function