Multi-sheet INDEX references

Not long ago someone here helped me with a similar problem, but now I'm in over my head! HELP! I think the solution involves INDEX formulae, but I really don't fully understand them yet.

I have a fairly complex (for me) spreadsheet that needs to make some non-sequential cell references from one sheet to another (please see the attached "PLP Example"). The problem areas are on Sheets Two and Three. In both cases, I entered text indicating the target cell in BOLD RED so it's easy to spot.

There are two areas where I am stumped.

On Sheet Two, I need to be able to copy and paste a block several rows so that the main entry is six rows apart (ie B13, then B19, then B25, and so on) while the reference in that frame is only 1 row apart (so, if B13 refers to Sheet One A1, then B19 would refer to Sheet One A2, and B25 would refer to Sheet One A3).

On Sheet Three, I need to do the opposite. I need to copy and paste lines so each line references data 6 rows apart on the target sheet. For example, U5 need to reference Sheet Two D19, U6 needs to reference Sheet Two D25, U7 needs to reference Sheet Two D31, and so on.

I think looking at the workbook is a great deal more clear than my rambling explanation.

Thanks in advance for any help!