Just FWIW:
$chr(37) $+ R (or % $+ R) = %R = Alt + R ;Obviously you cant send "%R" from a script, mIRC would try to evaluate %r as a variable
^{F4} = Ctrl + F4
More info at http://msdn.microsoft.com/library/default.asp?url=/library/en-us/script56/html/wsMthSendKeys.asp