Starting point - picture of pipe network. Ending point - calculation of longest route!

Hi,

I have a network of pipes (main line breaking into branches and sub-branches).

What I would like to do is calculate the longest route if I were to start at the beginning.

I have the CAD drawing which gives me all the branches and lengths.

I want to know how I should arrange this information in excel (should I make a table?) and how I can automate it so that if I put in the variables it calculates the longest length.

Does anyone know how this can be done??

Thanks!