Here are the general rules concerning Boolean functions:
Blanks are ignored (not either true or false)
Strings are ignored if part of an area ref or cell ref, otherwise they must be 'true' or 'false'
Numbers: 0 is false.
The enumeration value indicating the line style of a border in a cell,
i.e., whether it is borded dash dot, dash dot dot, dashed, dotted, double, hair, medium,
medium dash dot, medium dash dot dot, medium dashed, none, slant dash dot, thick or thin.