Change PivotField Properties with Empty Cache?

I'm trying to automate updating a set of pivot fields (making visible or
invisible, and changing the value of a page field). I'm ok until any one of
the fields has no records to display. When I make any changes manually, it
just displays "0" in the table, but if I use VBA code or record a macro it
gives me an error (presumably because there is no data?)
I could just enter some rows of dummy data just so the cache isn't empty for
any of the fields at any time, but surely there's a more elegant way of doing
it?

Any thoughts?