Shortest Routes

Hello! I want to schedule and find the shortest routes of ferry ways. For that, I made an Excel file, in which there are a route beginning column, so called 'from' , a route end column 'to' and time columns. For example I want to go from 'A' to 'C'. To be able to do this, I have to go to 'A' from 'B' and then from 'B' to 'C'. So, normally I think that I have to write a code like "if from==to" but I have to do this with rapidminer. I also have to find the proper time for the routes from the Excel file. So, how can I find these relationships of 'route beginning' and 'route end' by taking time factor also in consideration?
I would appreciate any help!