Matrix data hidden based on first month of another dataset

Hey there,This is my first post to the forum. Thanks much in advance.I have 2 tablix on on report with different datasets. The first is agent level by month. The second is the agent's supervisor metric by month where the dataset is pulling in year to date. More specifically, Jan 2014 to current month. My issue is that if a agent starts in Apr 2014 i want to restrict the Agent Supervisor metics data to only show Apr 2014 to current month.My attempt was to set the Visiblity on the group properties to the following:=iif(Fields!Month.Value<First(Fields!Month.Value, "InboundMetricsYeartoDate"),false,true)but the results only hide the line for Apr 2014 rather than all less than Apr 2014.Any ideas? Thanks