Probably I don't understand exactly what you are trying to do... but it seems to me that you could accomplish this using (drumroll, please...) you guessed it: Excel.

Make a list of tasks, say 1-9, more or less in order of importance.

Task 1
Task 2
Task 3
Task 4
Task 5
Task 7
Task 8
Task 9

Now add an index column in front of it, modeled on the Dewey Decimal system:

1.000 Task 1
2.000 Task 2
1.100 Task 3 (Dependent on task 1.000)
3.000 Task 4
1.110 Task 5 (Dependent on task 1.100)
4.000 Task 6
2.100 Task 7 (Dependent on task 2.000)
2.110 Task 8 (Dependent on task 2.100)
5.000 Task 9

Now sort the list by the index:

1.000 Task 1
1.100 Task 3 (Dependent on task 1.000)
1.110 Task 5 (Dependent on task 1.100)
2.000 Task 2
2.100 Task 7 (Dependent on task 2.000)
2.110 Task 8 (Dependent on task 2.100)
3.000 Task 4
4.000 Task 6
5.000 Task 9

The task you want to do next is always at the top of the list. You can have tasks dependent on tasks that are dependent on tasks that are dependent, ad-infinitum, that is if you had a new task that was dependent on task 2.100, you'd add it and index it as 2.110.

When a task is finished, delete it from the list. It isn't real pretty, but you could make it so with a bit of conditional formatting.

Of course, as I said, I probably don't fully understand what you're trying to do. But this is how I'd do it if I weren't retired and not under pressure to do anybody else's tasks. Oh, wait... SWMBO...

tanstaafl.