SSRS month &year formatting

I have a 2 field month and year from dataset. I have a "first" report linked with another report called "second".
Second report has start and end date in mm/dd/yyyy as a parameter. Now when i click on data points it should pass correct month and year to linked report.

Month & year comes from two different coulmns which will return like below

month  year
6       2011
12      2012

now when i pass this value to second report i want it in single value like below .Start should always take first day of the month and end date should always take last day of the month

start date ->06/01/2011
end date  ->12/01/2012

Any help is highly appreciated!!!