Alternate State Comparison in Background Color expression for a line chart

[brianhay]

I am trying to emulate the Set Analysis Example in the Sample QVD Executive Dashboard of the line chart where it displays the complete trend over a time period and then highlights a particular time section based on an alternate state.  The background color expression in the example is:

if([Book MonthYear]=[Book MonthYear],LightBlue(),LightGray())

I want the  [Book Month Year] in Alternate state A = [Book Month Year] in alternate state B, then LightBlue(),LightGray()

I'm having problems getting the syntax correct.

Please help