@Prompt Multiple select error

Hi,

I am using an @Prompt in UDT (it is being used to select a historical year) Essentially what I am looking to do is give this existing universe the ability to look back at any user selected 2 years of data and then run reports off of this data.

I am able to get the @Prompt to work for a single selection:

RADB.dbo.YMG_Fiscal_Periods.Fiscal_Year = @Prompt('Enter value for Historical Fiscal Year','N','RVU\Historical Fiscal Year',Mono,Constrained,Persistent,,User:0)

But when I change the @Prompt to try and use 2 years I get a syntax error in the WEBI Report:

RADB.dbo.YMG_Fiscal_Periods.Fiscal_Year = @Prompt('Enter value for Historical Prior and Current Fiscal Years','N','RVU\Historical Fiscal Year',Multi,Constrained,Not_Persistent,,User:0)

Any Suggestions of what I am missing?