vRO: Trying to find a way to have a drop down list of files to choose from

Hi Intelli-Gents -

I have a workflow that I am trying to create and publish in vCAC/vRA that does the following:

1) Launch catalog request item to "Import File"

2) The request form will have a search field for the VM to which the file will get copied (i.e. VC:VirtualMachine) - I've got this mastered

3) Additionally, the request form will have a drop down list of all the files in a certain directory on the vCO server (i.e. /nfs/repo/ folder) from which the user will select one file

4) Upon submitting, it will copy the file from the vCO server to the VM guest (which I can use the built in workflow for this)

So my current knowledge limitation is, how do I create a workflow that does number 3 above?  For further clarification, there are, for example, 20 various files that are in the /nfs/repo folder.  I want the user to be able to see all of them in a drop down fashion from which they can select one. 

As always I appreciate any help.

Karl