How to initiate OOB workflow with external(BCS connected) SharePoint list

Hi,

I have created a 3 tier .net application using .net framework like presentation,Business layer,Data access layer.Now i have to host these .net pages inside sharepoint 2010 farm.

Now the requirement is that I have to create out of the box workflows using BCS functionality by creating external list.How would i achieve that because for my knowledge external list does not support SharePoint OOB workflow.

Please suggest with a best elaborate answer.