Displaying Year & Month in cross tab


I want to display both year & month deatils in below format in Cross tab report in cognos 10.

format: Oct-12, Jan-2012,Feb-2013…like this in a single row …

I was able to get Month name in the report like Apr,May etc. But when I am trying to concat with year with ‘-’ , i am getting parsing error. I have used below exprn to combine year & month.

Cast( Business View.Aggr Month.Merchandising Month Name, varchar(3) ) + Business View.Aggr Merchandising Year.MERCHANDISING_YEAR

I am getting output as Apr2010, but i need to get ouput
Apr-2010,May-2010 like this…

How can I do this…please assist me ASAP.