(links go to documentation for MicroStation Update 16)
In the Flow Directives and Variable Directives section
the part on %if says:
See Operators for the syntax of <expression>. For example:
%if $(PHASE)=="Final"
However if you click the Operators link that page has no description of the == operator, or any of the other comparison operators. Descriptions for ==, <>, || and && should be added to that page (plus any other's i'm fogetting, i'm not sure if < or > work as comparison operators)