Not sure if I'm approaching my sub-report correctly with a variable?

I have a main report that is always ran in the previous plan year, so

{RPTFROMDATE}=01/01/2016 and {RPTTODATE}=12/31/2016

I have a subreport that is to be ran on 2017 and I am hoping to create a variable to send the 2017 ending balance to the main report.

First I was just trying to get the 2017 balance to show up correctly but I'm struggling with that part. I tried creating a variable to dateadd, and that didn't seem to work. I then tried to record select based on a formula that had a dateadd and that failed as well.

What would you suggest be the best approach?

Thanks,

Jordan