I haven't found any code examples on NavigationWhereClause on the
internet or in my book on A2010. Has anybody ever used that property
and have insight they can share?

Can one make visible/invisible navigation tabs on the navigation form?
Or reference a form on the navigation form from another form?

Salad wrote:

works.

Probably due to fewer people using Access.

Thinking about it, I would think one doesn't make tabs on a navigation
window visible or invisible.

The help in Access talks about the navigation buttons and properties but
for some reason provided no examples. Most likely the folks that
document the program at MS were kept out of the loop as well.