Yeah, unfortunately there's no way to exclude a number, but you can make it so if the number is rolled, you treat it as if it wasn't.
For example:
%SEVEN := 7 <---Do this where you declare variables
%ROLL := 1D10
IF %ROLL = %SEVEN THEN
BEGIN
%SEVEN := 0
END
So now if the event ever happens, it gets set to 0, so it can't happen again.