Multiple document upload control is an Active X control.In SharePoint we have “Upload.aspx” page in %\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\LAYOUTS. This page contains Multiple Document Upload Control which is used by all the sites in the site collection to upload multiple documents. I copied the content of this file into another file with the name upload1.aspx for safety.
Following are the arguments which this control accepts:
1. List GUID - GUID of the list in which the docs will be uploaded
2. Root Folder - If we need to upload the docs in the folders inside the libraries. Not using this parameters.
3. Source - Not using this.
4. MultipleUpload - 1 indicates to use multiple document upload control
We have put a button in the application pages and redirected it using Response.Redirect with these 2 parameters. This opened the multiple document upload control and while uploding the documents uploaded into the List selected as the first parameter.