Conditional Formatting in Calc

How can this be accomplished with LO 4.0.4.2?

Cell B1 should be protected UNLESS the leftmost two characters in A1 are "0/"

The sheet is protected. A1 is unprotected. B1 is normally protected. I unsuccessfully tried this conditional formatting in B1:

Condition: Formula is LEFT(A1,2)="0/"
Custom style "Unprotected" (based on style "Default" with "Protection|Protected" unchecked.

Other style attributes work just fine. I only have trouble with protection.

By the way, I really like the relatively new conditional formatting interface. Creating new styles on the fly is a breeze. I am using five conditions (six styles including the default) in some cells. I don't know what the limit is now. I know the old limit was three.