If there's no better solution, the only thing I can do at the moment is to add these two exceptions.
C:\Program Files
C:\Program Files (x86)
That really is a big hole in security you are creating as it encompasses a very large number of existing (and future) programs. If this really is an issue with office then that should be your C:\Program Files\Microsoft Office folder and possibly even more defined.
I'm not sure if the exclusions area would be enough, as it is possibly to exclude files but not their actions (such as running other functions), for that you would have to add say the winword.exe file.
That said 1, this UI is a bloody mess and I can find no such function (ignore process) that used to be in the Old UIs.
That said 2, I have in the past used the avast .ini files to add IgnoreProcess files, I don't know if this is the only route available, that would have to come from one of the avast team. An example of this that I used in the EmailShield.ini file. I don't know if this can be applied to the avast5.ini file or not.