Creating a New Music library view

[simbun]

In the tagUpdate file is there any way of specifying a match instruction to match a missing/empty/* tag?

The reason I ask is because I was going to write a script that created a crude "most recently added" filter utilising the tagUpdate functionality, but I couldn't get it to work so gave up.

I was trying to use something like:
@RECENTLYADDED=
&ALBUM=The SMiLE Sessions
&ALBUMARTIST=Beach Boys, The
&DATE=2011
=RECENTLYADDED=1

then use 'RecentlyAdded=1' in indexTags.