Hide data of collapsed matrix group

I have a matrix with date month on the rows axis. I want to hide all
but the most recent month. The data measures I am using are not
additive so I would like to hide the data for all collapsed groups.
Is this possible? I can't figure out how to reference a report item
to see if it is hidden or not.I got it...
--code to only show values in matrix where the group is visible.
=iif(
count(Fields!Num.Value) > 1
,""
, sum( Fields!Num.Value)
)
--code to set the most recent group to visible - default
=iif(format( Fields!Date.Value,"MMM yy") = format(
First(Fields!MaxDate.Value, "MaxDateForProject") ,"MMM yy")
, false,true)