I created a custom button for launching a new case with several fields pre-populated.  My agents are using Knowledge.  I want the new case to open with the Knowledge sidebar enabled in the service cloud console.  However, I believe I need to use some Java script containing the "srcUp" funciton to make this work.  Can anyone take a look at the custom button URL below and tell me how to include it in the proper Java script so it does not override the Knowledge sidebar?

"/500/e?
retURL=%2F{!AssetContactJunction__c.Id} &
def_asset_id={!AssetContactJunction__c.AssetId__c} &
def_account_id={!Asset.AccountId} &
def_contact_id={!AssetContactJunction__c.ContactId__c} &
00N40000001LeCs={!Asset.Product_Family_New__c}"

I want it to open as a subtab of the tab it launches from.