I'd like the users of my dashboards to be able to choose the date for which data is displayed, which can only be done with a parameter if you want to filter across several sources. I would like the user to only be able to choose from dates where data is available. This can be done by clicking "set from field" in the parameter range definition, but unfortunately this does not seem to update as the data is updated.
Any trick to solve this?
What you are asking for is quickly moving up to the top of my most wanted features list -- specifically, the ability for parameters to be updated / populated with new data at runtime.
We should post this to the new feature request part of the community.