In this recipe, we are going to develop a very similar Proposal Amount Approval workflow, but this time using Visual Studio 2010 and the Windows Workflow Foundation. This certainly requires a developer to do, but I hope you find during this exercise that it is overall not radically different or more difficult that its Visio / SharePoint Designer counterpart.
For added enjoyment, will add an Association Form that is an ASPX page – for you to be able to set the amount of the Approval Limit at the time you associate the workflow to the Proposal Library. This provides some configurable flexibility in the workflow – meaning the limit can be different for different Proposal libraries, and also not having to physically change the workflow code if you need to modify the proposal limit.