CloudWatch SingleStat Panel From Subset of Results

I’m trying to create a SingleStat panel to show ELB Unhealthy Hosts Count.
I can do this by adding this metric as a query to the panel, but this shows a single value for ALL ELBs in the account.
Can you limit this to a subset of ELBs?
I’ve tried to use a variable and a regex (below) but this returns multiple series which cannot be displayed by SingleStat.

Query: dimension_values($Region, AWS/ELB, HealthyHostCount, LoadBalancerName)
Regex: /.-test./

This can now be done in beta 5.3.0