Add a helper column
Put numbers in this column
Row that must stay together, give same number
Use this as the first sort key
best wishes

When you use "Subtotals" or "Group & Outline", you can sort the summary
(subtotal) rows, leaving the grouped rows intact, as individual units.

For example, to manually group some rows, enter A, B, C, ...etc down Column
A, say to A20.

In B1 enter
1/1/07

In C1 enter
=Rand()

Select *both* B1 and C1, and using the fill handle, drag down to Row 20.
While both columns are *still* selected, click,
<Data> <Sort>
Sort by Column C - <OK>

You now have Column A in order, with various dates in Column B.

Select rows 1, 2, and 3 by clicking in the row headers.
While these rows are selected,
hold down <Shift> and <Alt>
and hit the <Right Arrow>.

You have now manually grouped the first 3 rows, with A, B, and C.

Do exactly the same thing, grouping rows 8, 9, and 10, with H, I, and J,
and also rows 16, 17, and 18, with P,Q, and R.

You see the minus sign by rows 4, 11, and 19.
This means that *each* 3 row group will remain intact, and sort as a group,
depending on the value in rows 4, 11 and 19.

NOW ... select A1 to B20, and sort on Column B.

This puts everything in chronological order, *except* the individual groups,
which are dependant on the date in their respective summary rows.