It is better to use the conditional show feature to selectivly show or hide a sheet object. This works equally in all clients, whereas macros are client sensitive; and the conditional show operates automatically without needing to be triggered.
Go to Properties | Layout for the guage. Select Conditional and enter the following expression in the Conditional Show box:
=If(IsNull(<your guage expression here>), 0, 1)
Hope that helps
The conditional show on the entire gauge object works fine - thanks! - but it doesn't really fulfill what I want to achieve. The end users would probably be quite confused when the entire gauge is missing. I don't think they would interpret that as 0 actions, but rather as "something has gone wrong here".
I wish there was a conditional show on the indicator itself...
However, if I add a text object that is shown when the gauge is hidden I could inform the user about the 0 actions there. If I don't get any other suggestions on how to solve this problem I will likely go for that solution.