Flow through treatment string for one trip multilateral treatment

An adjustable tubular string nose uses axially relatively movable wedge segments to form a variable diameter ring shape using technology described in U.S. Pat. No. 7,128,146 in another context. The nose has a seat around a passage therethrough. After insertion of the nose into a first bore, typically a main bore, the nose is retracted out of the main bore and pressure against a seated bore in the nose expands the nose radially to a degree where re-entry into the main bore is precluded but entry into a lateral bore is still possible. The string advances onto a lateral no-go. This signals surface personnel to pick up and raise pressure to blow the seated ball through the seat to again open the passage in the nose. A seal stack behind the nose in advanced into a lateral seal bore and the treatment can then commence.