Thanks Matt, that worked. It didn't even occur to me to use another sheet in my dashboard to achieve that result. Appreciate the help and quick turnaround!
Not a problem! Sometimes placing a field on a sheet like this can really come in handy--cheers and good luck.
Joshua, one of the Tableau things that takes some getting used to is that worksheets are in many ways the functional mechanism that lets you achieve your goal. This is one example - where you need to create data that Tableau can display and a worksheet to display it in.
This is really, really weird for people coming from other programmatic or tool environments where functionality is accomplished with programming, scripting, or something similar. In your example it somehow doesn't feel right that this one simple, single little value for today's date needs to be a full fledged data field, that it's somehow polluting the 'real' data that one's out to analyze.
But it's the gift that keeps on giving. There are always surprises around the corner, people keep coming up with ways to munge up some data and organize it so that Tableau will produce the desired effect. And they publish their work so that others can accomplish the same thing.