I am not really following what you are asking for but in general you can use a select condition to get only 1 year of data (if you need full months you would need to account for that)
select criteria example:
table.datefield in dateadd('yyyy',-1,currentdate) to currentdate
then in your crosstab group on the date field set to per month
Edited by DBlank - 20 Feb 2015 at 6:38am