The company VNAV procedure is to set airfield elevation in the MCP, and only set the go around altitude DURING the go around?? What else does the landing checklist miss out?
The altitude set in the MCP window is temporary, it just needs to be something lower than where you are - most operators pick MDA rounded down. You should never actually reach it. Once you're 300' below missed approach altitude you can reset the missed approach altitude and VNAV will ignore it.