No, I couldn't give you an adequate figure. However, I would refer you to the Securing Afghanistan's Future report, a report I was actually involved in, an Afghan government report released in 2004, which was basically a recosting study to determine the cost of the reconstruction process.
It determined that it would cost $27 billion over five years, from 2004. I imagine this figure is probably still somewhat accurate today, although that doesn't take into consideration costs associated with international troop deployments and any unforeseen circumstances that could arise.