Let's say I have 30 entries out of 1,200 in my database that have "use alternate form" set to "Tutorial1.mxf" I want to clear that value. How to do that? Is there some sort of null character that can be used?

Try this:

Retrieve all those entries into your current list for the address book window.

Click Edit>>Select All, then Edit>>Global Edit.

Then go to the field in question and hit the space bar. Then apply the edit. That should blank the field.

thanks, that seems to work