Capturing URL parameter value in Standard BSP

Hi,

We have a standard Marketing Plan BSP that is created using the Web Interface Builder in the SEM system. This BSP has plan ID which is a drop down and based on the selection the BSP reacts.

Now we are incorporating this BSP in the Enterpise Portal. We need to pass the PlanID as a query string parameter in the BSP url. I need to know how the BSP application can take this parameter from the query string and act accordingly. Keeping in mind that this is a standard BSP which SAP has created. The only leeway we have is to customize the PlanID variable using the transaction bsp0. thanks.

Any tips will be useful.