[This is preliminary documentation and subject to change.]
This is the Property property of the MsiUIPreview object. This read-write property represents the string value of a named installer property, or, if it is prefixed with a percent sign (%), the value of a system environment variable for the current process. This is exposed to allow proper display of dialog boxes that are dependent upon property values. Either string or integer values may be supplied. A non-existent property or environment variable is equivalent to its value being Null.
object.Property(name)