You can not select multiple files for insertion to a container field in any version of filemaker, so your entire process is redundant. You've noted you've bypassed this on the desktop with a plugin, I'm assuming troi file or MBS. WebDirect will probably not likely support client-side plugins anytime soon.
What you could possibly do is:
Set Variable [ $id ; parenttable::primarykey ]
Go To Layout [ containertable ]
set field [ containertable::foreignkey ; $id ]
Insert File [ containertable::containerfield ]
Exit Loop If [ get(lasterror) = 1 ] //IE if user cancelled insert file
If [ IsEmpty (containertable::containerfield) ]
Delete Record, no dialog //Removes the last blank record.
Go To Layout [ original layout ]
The above would allow you to create a loop to add multiple files to a related parent record, but it's still within the confines of the "one at a time" FM file selection.
Of course, the above could be made a lot more elegant with more error checking and a better loop process, but it's just a basic idea.
You could upload a ZIP file and use a plugin on the Server to export, parse names, unzip, and then read in one at a time... using insertFrom URL file:\\\filenameHere.ext
Thank you guys
The client had asked for adding multiple files from a file dialog so I wanted to make sure I wasn't overlooking anything when I told him that this method is not an option.
I will be telling them to zip larger sets of files while smaller numbers may be dragged into a portal list of related container fields.
On the local end I will be using FM client anyway so there I can play around a bit more with options.
And I'm using the BE plugin on the client side at this time.