What you want is to take out a protein directly from the gel or from a nitrocellulose or PVDF membrane, once it has been transferred, for example in order to sequence it?
You can cut the band from the gel with and put it in an eppendorff with few microliters of the loading buffer for electrophoresis. You can then chop the piece of gel up, vortex it and also let it in contact with the buffer for a while fir sonication which helps as well as the protein band can pass into the buffer. Then just spin the eppy down and recover the buffer with your protein. You can than concentrate it, dialyse it or reload it directly on another gel if you want to run it again.