Your line:
$SK SetFocus ("SENDKEYS")

is missing the =
$SK= SetFocus ("SENDKEYS")

but really, that is not good enough anyway. You need to put it into a wait loop.
code:
Break on
Run 'notepad'
while SetFocus('Untitled - Notepad')<>0
  "."
  sleep 1
  $Index = $Index + 1
  if $index > 20
    $RC = MessageBox("NOTICE!" + Chr(13) + "Notepad did not open within a reasonable time!"
    + Chr(13) + "Please notify the HelpDesk at ext. 1234","Notepad example",48,60)
    goto finish
  endif
Loop

$RC=Sendkeys('Hey, it worked!')
_________________________
Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.