DAX Query to Fitler rows by Date

Hi

I'm connecting to SQL Server Analysis Services Importing Data and it's returning rows that are several years old and I only need data for the last year. The connection screen for Analysis Services has a section for entering MDX or DAX. From the Source I have a Month and Year column to work with.

First can I use a DAX query to filter the rows returned to be within the last twelve months?

I have tried the following DAX query in the query input box but I get the error it is not a valid MDX or DAX query 

FILTER(Sales, DATE('01', Sales[Month], Sales[Year]) <= EDATE(TODAY(), -12))

Any help or information gratefully received

Thanks

Ven