I using SharePoint Designer to create a workflow. I'm trying to get at
a subfolder in a document library in the "Define Workflow Lookup"
dialog. There are two issues with this:

1) I can't look up items by URL Path. If I look up by Title, I can
output the URL Path, but selecting by path doesn't work. What fields
can/can't I use?

2) I can't get at any subfolders. I can get at the top-level folder,
but the subfolders don't seem to be available. Noticed the same things
is true when looking at the data for a document library in the "Data
Source Library" in Designer.

To clarify, the workflow is on a different list, not on the document
library.

Also, I know how to do this through the object model, the question is
how to do it in SharePoint Designer without deploying code to the server.