Customizing the "Upload Document" Form in SharePoint 2010 based on Content type

When you click on the name of a library, go to the documents tab, click on "upload document".

An upload form appears that is created using the dialog framework. The 1st choice on the form is content type.

I need to instead launch a custom infopath form that will allow me to dynamically populate a 2nd dropdown box on the page after the content type (still 1st) dropdown is populated.

I feel like I'm really grasping at straws here. At this point I could use a reference to a relevant section of a book, a link to a relevant post or even just the correct terms to put into a google search. What is the correct name for that form?

I found this which seems to teach you how to insert a customized aspx form: http://microsoftsharepointandbeyond.blogspot.com/2009/10/customizing-ootb-sharepoint-forms.html But I'd really like one that uses Infopath instead.

Any advice or direction you can provide would be greatly appreciated.

I'm pretty sure doing this with infopath is not possible, the forms are bound to a (codebehind) class in the SharePoint object model, which handles the actual upload (add to list, set field values etc. etc.).

A custom aspx page would be possible though, exactly as the post you mentioned descibes. I agree with the post's author that an HttpModule would be best, because:

• editing the OOTB upload.aspx in the 14 hive would make your environment unsupported (i.e. if anything brakes, MS will have you revert your farm to a supported state before they come and help you.
• The next time you install an update for sharepoint, your changes could be overwritten.