Need to move cells to the left in an outline

[HowdeeDoodee]

I am working with a 300 page outline going 7 levels deep. I need to indent the lines beginning with [---] over to an appropriate level. The appropriate level is determined by the row above the addendum lines. Here are a before and after view of what I need to do.

Before

I. First Category.............................................
.....A. First subline........................................
.....B. Second subline........................................
.....C. Third subline........................................
...................................[---] First addendum line.....
...................................[---] Second addendum line.....
...................................[---] Third addendum line.....
..........1. First subsubline...................................
..........2. Second subsubline...................................
...................................[---] First addendum line.....
...................................[---] Second addendum line.....
..........3. Third subsubline...................................
...............a. First subsubsubline..............................
...............b. Second subsubsubline..............................
...................................[---] First addendum line.....
...................................[---] Second addendum line.....
...................................[---] Third addendum line.....
.....D. Fourth subline........................................
..........1. First subsubline...................................
...................................[---] First addendum line.....
...................................[---] Second addendum line.....
...................................[---] Third addendum line.....
...................................[---] Fourth addendum line.....
..........2. Second subsubline...................................
..........3. Third subsubline...................................
..........4. Fourth subsubline...................................
...................................[---] First addendum line..........
...................................[---] Second addendum line..........



After

I. First Category.............................................
.....A. First subline........................................
.....B. Second subline........................................
.....C. Third subline........................................
..........[---] First addendum line.....
..........[---] Second addendum line.....
..........[---] Third addendum line.....
..........1. First subsubline...................................
..........2. Second subsubline...................................
...............[---] First addendum line.....
...............[---] Second addendum line.....
..........3. Third subsubline...................................
...............a. First subsubsubline..............................
...............b. Second subsubsubline..............................
....................[---] First addendum line.....
....................[---] Second addendum line.....
....................[---] Third addendum line.....
.....D. Fourth subline........................................
..........1. First subsubline...................................
...............[---] First addendum line.....
...............[---] Second addendum line.....
...............[---] Third addendum line.....
...............[---] Fourth addendum line.....
..........2. Second subsubline...................................
..........3. Third subsubline...................................
..........4. Fourth subsubline...................................
...............[---] First addendum line..........
...............[---] Second addendum line..........

Thank you in advance for any replies.