John,
Yes, there are probably multiple ways to do it some better or more
efficient than others. Here's one I just threw together in my mind. It
may be a bit klugy but it should at least get you there. Note: I did not
have time to test it.
1. Copy the ID field to a spare number field (e.g. Number1).
2. Develop a filter to segregate the subset of tasks you want sorted and
apply the filter
3. Sort the file by the Start Date. (In the filtered view you will only
see the desired tasks sorted but the whole file will be sorted at this
point - stay tuned).
4. In the sorted filtered view, rearrange the value in the spare number
field to be in order
5. Remove the filter (i.e. apply the "all tasks" filter)
6. Finally, re-sort the file in ascending order on the spare number field
Note that the above process will not segregate the subset of tasks (not
a stated requirement) but the file will be sorted as you wanted.
Hope this helps.
John