How can NinjaCal show me on which days I have events?
You can send NinjaCal a list of dates to highlight so it is pretty easy to have NinjaCal display all the days on which you have events.
To see the highlighting in action, check out the "Scripted Actions" tab of the NinjaCal example file. Action number three, "Select a List of Dates" shows how a carriage return separated list of dates can be passed into NinjaCal.
So let's say you're booking a conference room and want to see all the days when it is already booked. Assuming you have a relationship to a table containing all these events, you can use the List() function to build a carriage return separated list of dates and then send these to NinjaCal. You'd simply call the NinjaCal script with the following script parameter:
"selectDate" & "¶" & Quote ( List ( RelationshipToEvents::EventDate ) ) & "¶" & "-f"