Changing flag date or time on many messages at once?

This is one I haven't tried to fix before. I have a special use for
Outlook. Besides regular messages, I send myself "To Do's" to and
from home marked with a special phrase when it's a To Do that has
rules that mark it with a flag, etc. In either work or home, a lot of
those To Do's need to be deferred to a different time or day. It's
been tedious as I have to change each manually. Now I made it easier
some time ago by putting a flag option right on the toolbar so at
least I don't have to open each message. The preview pane is on for
this folder and I then easily change to whatever new date/time it
should pop up.

Is there a way to have more automated control over this? What would
be nice is to be able to select any or all of the msgs and then to
change the date or time globally for all of the selected items. Is
this possible in any way?

TIA. D