You need to simulate the ELSE with two IFs with each condition reversed. Be aware that if the first IF changes the data used in the test for the second IF, then you might see both IFs being true (ie. not a true else)
eg: # message is a note IF M0 == 90 END # messages is not a note IF M0 != 90 END
> By the way, there is any way to invert the value of a boolean?
I tend to use xor operator '^' to do that (and use convention false = 0 and true = 7F)