ssrs multi parameter wrapped with Month() function

I have a prameter in my ssrs report called @Period, the user can select multiple dates ,i.e  1/4/2012, 1/5/2012, 1/1/2013 in the prompt

In my Dataset my query goes like so :

select columns,...
from table
where month_int  IN  Month(@Period)   -- I have the month() function around the @Period
and  Year_int   IN  Year(@Period)

I get an error saying that Month() expects single value, How can I do something to @Period to give me for month ('4','5','1') 
and for year ('2012', '2013')

thanks,