Question about post workout eating..

I know that you are supposed to eat after working out, but what constitutes the end of a work out?

I work out in my apartments and sometimes I do cardio, sometimes I do weights, sometimes I do both, and not in the same order.  This is because there is only 1 working ellptical, 1 treadmill, and then a few weight machines.

So what happens if I do weights first then end up walking on the treadmill for 45 minutes, would the end of the workout be the weights or the end of the treadmill? 

The end of the workout would be when you are done your cardio. I'd suggest taking any protein or BCAA's directly after lifting, though.  It'd also be okay to eat at that point if you wanted to. (Assuming you can run on a full stomach!)