[Data Manipulation] Duplicate String Pattern, Alter and Append Value to Existing String

The spreadsheet (attached) contains a list of 843 text strings that contain value trees delimited by commas, e.g: ALFA ROMEO > 156, ALFA ROMEO > 156 > 932, ALFA ROMEO, ALFA ROMEO > 156 > 932 > Sep-97 - Sep-05 The objective is to add a new value to the value tree list, "Unknown". Unknown needs to be applied to every third level tree, and any subsequent children. In the example given, the following would be a third level string: ALFA ROMEO > 156 > 932 This value would need to be duplicated, with the third value being replaced with "Unknown": ALFA ROMEO > 156 > Unknown In the example given, the following would be a fourth level string: ALFA ROMEO > 156 > 932 > Sep-97 - Sep-05 This value would need to be duplicated, with the third value being replaced with "Unknown": ALFA ROMEO > 156 > Unknown > Sep-97 - Sep-05 These values would be appended to the initial value in the column next the original labelled "Result" For example, the initial snippet would become: ALFA ROMEO > 156, ALFA ROMEO > 156 > 932, ALFA ROMEO, ALFA ROMEO > 156 > Unknown > Sep-97 - Sep-05, ALFA ROMEO > 156 > 932 > Sep-97 - Sep-05, ALFA ROMEO > 156 > Unknown The project can be completed using any combination of Excel formula or regex, with the handover document being a completed .csv Shorthand: Replace y with "Unknown": x > x > y, x > x > y > x, ... x > x > y, x > x > y > x