Capturing Lead Source from BrightTalk?

[Anonymous]

Anyone have any suggestions for how to capture information such as Lead Source and Last Lead Source from BrightTalk created leads?

The Issue
In general, we use a combination of URL parameters and Filled out form workflow rules to populate source related fields whenever a lead fills out a form or is imported. Because the BrightTalk form is its own form and the data comes in nighty via the connector, I can't figure a way to populate a unique lead source when that data arrives. Is there some kind of URL parameter equivilent for BrightTalk?

Use Case
Using another provider, we used to provide trackable links (w URL Parameters) to partners to promote our webinars when the landing pages were hosted at Marketo. If the form got completed where Last Lead Source = Partner name, we trigger a partner alert, etc. With BrightTalk, we only get the standard registration info nightly.

[Edward_Masson]

I take it that based on the package/service paid with BrightTalk, customizing their form will cost extra? 
I'm not sure of any other way other than URL prams.

Interesting to see what else can be used as a work around.