how to show calmonth range for this year and last year in text column

Hi gurus

in my report user enter a calmonth range in selection menu. lets say they enter 01/2011 to 06/2011. now one column in my report shows the sales for this range 01/2011 to 06/2011. and than the second column shows the sales from last year for this range. ie for 01/2010 to 06/2010.

now i want to create a text variable that shows these ranges for both the respective columns. I was able to create one for 01/2011 to 06/201 but how do i create the TEXT Variable for the previuos year column ?

thanks