How to conditionally concatenate in Excel 2016

Hi ChemistB,

Thanks for this. Actually, I made a mistake. Instead of concatenating Node B to Node A I want the opposite(instead of concatenating row 3 to row 2, I want row 2 to row 3). Please see the example_corrected spreadsheet.

How would this work now?

If you take my suggested approach, you can have the same formula in C2 (copied down) and this one in B2:

=IF(OR(C2=MAX(C:C),C2=""),"",INDEX(A:A,MATCH(C2+1,C:C,0))&"-"&A2)

which just reverses the order.

Hope this helps.

Pete