I'm interested in seeing if it's possible to use a workflow to dynamically set a choice field's available options. In essence, this effort is seeking to provide a cascading effect without using the well-established jQuery approach. For example, if custom fields in my library reference a separate list containing the typical country/city hierarchical setup, choosing something in the library's Country field should dynamically alter the City field to display only cities within the selected country.
So far I have the workflow set up so that it builds a dynamic string of matching options, delimited by semicolons and with preceding hashmarks on all but the first item. That is, selecting "United States" in the country field returns a string of "Atlanta;#Los Angeles;#New York City". But the Update Item action that is supposed to set the target choice field to the contents of the dynamic string doesn't seem to affect the field. It still contains the preset choices.
The intent is to try (without resorting to coding) to find a way to provide this cascade effect within the datasheet view of a library. I realize in advance the datasheet view is an ActiveX component and that will likely cause the greatest amount of trouble, but it *seems* like this could work, and I want to check with the community of experts before moving on to other possibilities.