i think it's as simple as changing the editable property on your store and/or editorgrid. it probably gets set when the store loads, but you could listen for that even and change it. you could add your column at this point too.

if you want to get more involved, look at what ehrStore.js does in the EHR module. That extends the labkey store. the onProxyLoad method listens for when the query metadata is returned by the server. at this point you can modify or augment it. it's a pretty low level way to hook into things.

out of curiosity, what's the point of editing 1 column if it isnt going to be submitted?