How to set up the Query in Templating?

I have set up the host and program.
In Query Options,the query is label_values(host) and other is label_values(program).
But they are not related. I mean I first select the host, then select the program which in this host.
I try to use label_values(host,program), but it does not work.
Can you help me?

Did you get this working?

Can you give more details on this. How does it not work?

Thank you for your reply.
When I use label_values{host}, I can get About twenty options.
When I use label_values{post}, I can get every process I name, like bs_0001, bs_0002, …
When I use label_values(host,program), the Preview of values is none, and the metric is {host="$host", program="$program"} in graph is no data.

I want to select program only in selected host.
Thanks again.