Hey Paul,
Not ignoring you .. just trying to think of a way to accomplish what you're asking for ...
I can't think of any way to do it without code changes. However, if you're up to code changes, here's my thoughts.
1. take a look at the Dashboard code. It has logic to query the modules table and find all of the repository modules that are installed. It uses that to populate the dropdown list of repositories so you can associate a dashboard with a specific instance of a repository module somewhere on your site.
2. you'd have to add a new tag to the form processor to inject a combo box on the upload form and populate it with a list of repositories, similar to what the dashboard is doing. that would allow your users to select a specific repository to upload the item to
3. when submitting the item, you'd have to replace the current "ModuleID" with the module id of the selected repository from the dropdown. Again, look at the repository dashboard code, that's pretty much what it does, stores the module id of the selected repository module in the drop down list
Those changes should do it. When a user uploads an item, they could select a repository, and when the back end function is called to add the item, the module id of the selected repository will be passed as the module id and the stored item will be associated with that specific instance.
:)