> but how we're going to detect the intention to edit?

You are right - no need to change Text.ControlSourse. Fully enough to define Column.ControlSourse.
As about "intention to edit" - hmm - how about a simple check of Text.Click or Text.DoubleClick or Text.KeyPress to determine if Enter pressed ? Or may be you prefer some refined method ? :) Some very special buttons for editing, some complex keypresses sequence to be sure, that user want to edit something and nothing else ?