I did never manage to get these flags working correctly in all cases. In particular, Lua scripts are always triggered in most cases. Also, on instances there is a problem on startup. It will trigger a load of modulators on startup sending a big mess to midi-out. Only way for me: use toggle variabal as dnaldoog suggested. I use it like this:
if doNotSend then return end
This is short and painless.. more or less.